JPH0971893A - Corrosion-resistant ferrous member and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the corrosion resistance of a ferrous substrate even if a hard-chromium plating layer is thin. SOLUTION: A ferrous substrate such as a cylinder rod is plated with hard chromium, high-frequency heated or heat-treated by baking, impregnated with resin and buffed. In this case, cleaning is applied after plating and/or heat treatment to produce a corrosion-resistant member. The plated substrate is cleaned with hot water, acid, etc., and the heat-treated substrate is cleaned with acid. The heat treatment is conducted at 100-500 deg.C in many cases. The impregnation is carried out under reduced pressure by using a thermosetting resin. The rating number of the corrosion-resistant member thus obtained is controlled to 9.5-10.0 when the CASS(copper accelerated acetic acid salt spray test) test of JIS H8502 is conducted for 96hr.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a corrosion-resistant iron-based member and a method for manufacturing the same. In particular, the present invention relates to a method for producing a corrosion-resistant member capable of imparting high corrosion resistance to an iron-based base material such as a cylinder rod used in construction machines, industrial machines, industrial vehicles and the like.

[0002]

2. Description of the Related Art Conventionally, cylinder rods such as piston rods have been used in hydraulic machines for construction machines such as power shovels. The rod that slides on the cylinder is required to have characteristics such as high hardness and wear resistance, and high dimensional accuracy including surface accuracy. Therefore, the cylinder rod is usually manufactured by subjecting a rod made of an iron-based material to hard chrome plating. However, unlike other electroplating layers, a large number of defective portions such as cracks, pinholes, and pits are generated in the plating layer formed by hard chrome plating even if the thickness of the plating layer is about 100 μm. Therefore, the hard chrome plated rod is prone to corrosion and rust despite having various excellent characteristics. Particularly, in the presence of chloride such as sodium chloride, an acid, or in a high temperature and high humidity environment, the rod is significantly corroded due to the numerous defective portions. When the rod is corroded, sliding on the cylinder causes scratches, which may cause oil leakage.

In order to prevent corrosion of the hard chrome plated product, a rust preventive agent is applied and penetrated into a defective portion such as a crack, but this is not a fundamental solution. Further, in order to prevent corrosion of the hard chrome plated product, a plating layer having a thickness of about 0.05 to 0.1 mm is formed. However, if the thickness of the plating layer is increased, the productivity will decrease.

Japanese Examined Patent Publication No. 3-14913 discloses a method for performing high quality mirror chrome plating, which uses a micro crack type chrome plating bath, and the surface of an iron base material is about twice as thick as the finish plating layer. A thick plating layer is formed under severe conditions (40 to 6 times higher than the upper limit of standard operating temperature).
After baking at a high temperature of 0 ° C. for 40 to 50 hours,
A method of removing 40 to 50% of the plating layer by polishing, baking under mild conditions (20 to 30 hours at a temperature 10 to 20 ° C. higher than the upper limit of the standard temperature for use), and finish polishing is disclosed. There is. However, in this method, it is necessary to form a thick plating layer and to remove 40 to 50% of the plating layer, which is not economical and requires a long time for the plating process and the removal of the plating layer. Moreover, it takes a long time to perform baking twice. Therefore, the productivity of drums, rolls, etc. is significantly reduced. Further, the above-mentioned prior art documents do not describe anything about corrosion resistance.

In JP-A-60-33369, a metal is chromium-plated and heated at 120 ± 10 ° C. for 15 to 30 minutes to remove hydrogen gas generated by the plating. And a method of applying a corrosion protection composition composed of a mixture of 80 to 20% by weight diallyl phthalate. However, the obtained metal member does not have sufficient corrosion resistance, as shown in a comparative example described later.

In order to improve the corrosion resistance of the cylinder rod, the applicant of the present invention has proposed in Japanese Patent Laid-Open No. 4-160197 that the cylinder rod is plated with hard chrome and baked. In addition, JP-A-7-7078
No. 7, the corrosive iron-based base material is 10 to 100 μm.
Hard chrome plating to a thickness of about 150 ℃ (17
After heat treatment at a temperature of 0 to 600 ° C.), a resin or a sealing agent is impregnated under reduced pressure to cure the resin or the sealing agent, and buffing is performed to provide high corrosion resistance. . These methods can impart high corrosion resistance to a highly corrosive iron-based substrate, and are useful for producing a cylinder rod or the like used under severe conditions. However, in these methods, the corrosion resistance of the iron-based base material may fluctuate due to factors whose cause is unknown, and the yield of the corrosion-resistant iron-based member may decrease.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a corrosion-resistant iron-based member in which extremely high corrosion resistance is surely imparted even if the hard chrome plating layer has a small thickness, and a method for producing the same. Especially. Another object of the present invention is to provide a method capable of reliably providing corrosion resistance equal to or higher than that of stainless steel, even if the iron-based base material has corrosiveness, and capable of producing a corrosive iron-based member with high yield. To provide. Still another object of the present invention is to provide a method of manufacturing a corrosion-resistant iron-based member useful for manufacturing a cylinder rod having the above-mentioned excellent properties.

[0008]

In order to achieve the above object, the inventors of the present invention have made earnest studies, and as a result, in the above method including a hard chrome plating step, a heat treatment step, a resin impregnation step, and a finishing step, hard chrome plating The present invention has been completed by discovering that if a chromium-plated product (workpiece) is subjected to a cleaning treatment after the heat treatment step and / or the heat treatment step, extremely high corrosion resistance can be surely imparted to the corrosive substrate even if the heat treatment temperature is low. did.

That is, in the method of the present invention, a plating treatment step of plating a corrosive iron-based base material with hard chromium, a heat treatment step of heat treatment, an impregnation step of impregnating a resin or a sealing agent, and a buffing finishing step. A method including and
A corrosion-resistant iron-based member is manufactured by performing a cleaning process after the plating process and / or the heat treatment process. In such a method, at least the cleaning step after plating (hereinafter sometimes referred to as the first cleaning step) and the cleaning step after heat treatment (hereinafter sometimes referred to as the second cleaning step) Either one of the cleaning steps may be adopted, but it is effective to adopt at least the second cleaning step. In the second cleaning step, an acid such as an inorganic acid may be used for cleaning. These washing steps may be performed alone or in combination. Such a cleaning process imparts extremely high corrosion resistance. As the resin or the sealing agent, a thermosetting resin or a sealing agent which is composed of an acrylic or methacrylic oligomer or monomer and has a viscosity at 25 ° C. of 1 to 50 cps can be used. Impregnation with can be performed under reduced pressure (for example, under reduced pressure of 0.1 to 100 Torr). Further, in the buffing step, a hard chrome plating layer of about 5 to 95 μm may be formed. In the method of the present invention, a corrosive iron-based cylindrical rod such as a cylinder rod is plated with hard chrome, and
A plating treatment step of forming a hard chromium plating layer of 100 μm, a heat treatment step of heat treatment at a temperature of 100 ° C. or higher, an impregnation step of impregnating a thermosetting resin or a sealing agent under a reduced pressure, and an impregnated resin or sealant. It is a method including a hardening step of hardening a stopper and a finishing step of buffing, and also includes a method of manufacturing a corrosion-resistant iron-based member by washing with an acid after at least a heat treatment step. In these methods, by adopting the cleaning step, high corrosion resistance can be imparted even when heat treatment is performed under relatively mild heat treatment conditions. For example, the heat treatment temperature is 100 to 500.
The temperature may be in the range of about 0 ° C, and the heat treatment may be performed at a temperature of 100 to 300 ° C for 30 minutes to 12 hours.

According to the method of the present invention, extremely high corrosion resistance can be imparted. For example, when a Cass test specified in JIS H8502 is carried out for 96 hours, a corrosion-resistant iron-based material having a rating number of about 9.5 to 10.0. The member can also be obtained. Therefore, the corrosion-resistant iron-based member is suitable as a member requiring high corrosion resistance even under severe conditions, for example, a cylinder rod such as a piston rod.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

[Iron-based substrate] The iron-based substrate is various iron-based materials such as low carbon steel, high carbon steel, hardened steel, high speed steel, chrome steel, nickel steel, nickel chrome steel, nickel chrome. -Can be formed of molybdenum steel, tungsten steel, etc.
Since the method of the present invention can impart a significantly improved corrosion resistance to a corrosive member, the present invention is suitably applied to a corrosive iron-based substrate. The shape of the iron-based substrate is not particularly limited, and may be a flat plate shape, a curved plate shape, a polygonal cross section, a cylindrical shape, a hollow shape, or the like. The iron-based base material that is required to have high corrosion resistance includes a rod-shaped base material such as a cylindrical rod (for example, a cylinder rod such as a piston rod).

Prior to the chrome plating, the iron-based base material is usually subjected to a pretreatment step. In this pretreatment step, the iron-based base material may be generally subjected to a degreasing treatment by an organic solvent, an alkali immersion, an alkaline electrolytic degreasing treatment or the like, and if necessary, a pickling treatment with an acid such as hydrochloric acid or sulfuric acid.

If necessary, the iron-based base material may be subjected to a polishing step prior to the chrome plating. The iron-based base material is polished by a conventional method, for example, cylindrical polishing (ring buff) having a large polishing force, vertical polishing, etc .; rough polishing such as emery buff polishing, belt polishing, flap wheel polishing; cotton buff, sisal buff, and combinations thereof. Further, medium polishing and finish polishing can be performed individually or in combination. The medium polishing and the final polishing may be of a closed face type, an open face type or a unit face type. If cleaning treatment is performed after the chrome plating treatment step and / or the heat treatment step, especially after the heat treatment step, high corrosion resistance can be obtained without polishing the corrosive iron-based substrate for adjusting the base. Therefore, by adopting the cleaning step, the polishing step for adjusting the base of the base material can be omitted, which is industrially advantageous in increasing the production efficiency of the corrosion-resistant iron-based member.

Prior to chrome plating, the iron-based substrate may be subjected to an etching treatment by anodic oxidation for adjusting the plating base. The etching treatment by anodic oxidation is carried out, for example, by electrolytically treating the iron-based material as an anode at a temperature of about 30 to 60 ° C., a current density of about 10 to 50 A / dm ² and a time of about 10 to 600 seconds. You can Instead of the etching treatment by anodic oxidation, or together with the etching treatment by anodic oxidation, an acid immersion treatment of immersing in hydrochloric acid, sulfuric acid or the like may be performed.

[Chromium Plating Process] The iron-based substrate is subjected to hard chrome plating. The composition of the chromium plating bath is not particularly limited, and a conventional plating bath can be used. As the plating bath, for example, chromic anhydride Cr
Sargent bath containing O ₃ and sulfuric acid; chromic anhydride CrO
₃ , a silicofluoride bath containing sodium silicofluoride, potassium silicofluoride, or the like in addition to sulfuric acid may be used.
Further, the chromium plating bath may contain at least one component such as silicofluoric acid, ammonium fluoride, strontium sulfate, citric acid, tartaric acid, oxalic acid and formic acid. The plating bath is usually 0.1 to 3 g / L of trivalent chromium
Often includes the degree.

The ratio of chromic anhydride and sulfuric acid in a plating bath, for example, a Sargent bath is usually about 100: 0.8 to 1.5 (g / L) chromic anhydride: sulfuric acid. Chromic anhydride 100 g / in order to improve corrosion resistance
The amount of sulfuric acid with respect to L is 0.9 to 1.3 g / L, preferably 1.0 to 1.25 g / L. As the amount of sulfuric acid decreases, the covering power improves, but the corrosion resistance tends to decrease, and as the amount of sulfuric acid increases, the corrosion resistance improves, but the adhesion and the uniformity of the plating layer tend to decrease. The plating bath may be a high-concentration bath, a standard bath, or a low-concentration bath, and the chromic anhydride concentration is usually 100 to 4
The amount is 00 g / L, preferably 150 to 350 g / L, and more preferably 200 to 300 g / L.

In hard chrome plating, a lead alloy, iron or the like can be appropriately arranged and used as an anode, and an auxiliary cathode, a shielding plate or the like can be used in order to make the plated portion uniform. The plating conditions can be selected according to the composition of the bath, etc., and the plating temperature is usually 20 to 70 ° C., preferably 4
The temperature is about 0 to 65 ° C., the current density is 10 to 100 A / dm ₂ , and preferably about 30 to 60 A / dm ² . The plating time can be selected according to the bath temperature, current efficiency, desired plating film thickness, and the like.

The thickness of the hard chrome plated layer formed by plating can be selected within a range that does not impair the corrosion resistance.
The thickness is 200 μm, preferably 10 to 150 μm, and more preferably 10 to 100 μm. A particularly preferable thickness of the hard chrome plating layer is 15 to 75 μm (for example, 2
5 to 75 μm), especially about 15 to 60 μm. If the thickness of the hard chrome plating layer is small, the corrosion resistance tends to decrease, and if it is too thick, not only is it uneconomical, the plating requires a long time, and the productivity decreases. The plating layer having the thickness as described above can be formed, for example, in about 1 to 2 hours, which is advantageous in industrially efficiently producing the corrosion-resistant iron-based member.

According to microscopic observation, the hard chrome plating layer has many cracks and pinholes which cause corrosion. Further, as described in the above-mentioned prior document, when the hard chrome plating layer is heat-treated, cracks generally grow. However, by combining the step of heat-treating the iron-based base material subjected to the hard chrome plating treatment, the impregnation step of impregnating with the resin, and the first cleaning step and / or the second cleaning step, the film of the hard chrome plated layer is formed. Even if the thickness is thin, extremely high corrosion resistance can be surely imparted to the iron-based substrate, and the yield of the corrosion-resistant iron-based member can be dramatically improved.
Furthermore, as in the above-mentioned prior art, a hard chrome plating layer having a large thickness is formed, and it is used as a cylinder piston rod of a construction machine or the like used under severe conditions without performing polishing and baking twice. However, the corrosion resistance is extremely high.

[Washing Step] A feature of the present invention is that after the hard chrome plating treatment, the plated article is treated by a series of steps including a heat treatment step, a resin impregnation step, and a washing step. The point is to reliably and dramatically improve the corrosion resistance of. Compared to the combination of the heat treatment process and the resin impregnation process, by combining the cleaning process with each other, even if the thickness of the hard chrome plating layer is small, it is possible to surely impart high corrosion resistance to the corrosive base material, and high quality hard The yield of chromium plated products can be greatly improved. The cleaning process may be performed after either one of the plating process and the heat treatment process. Of these cleaning steps, the second cleaning step after the heat treatment step seems to have a greater effect on the corrosion resistance than the first cleaning step after the plating processing step. Therefore, it is preferable to wash the heat-treated product in at least the second washing step of the washing step,
The first cleaning step is not always necessary. In order to surely impart higher corrosion resistance, the first cleaning step and the second cleaning step
It is preferable to perform the washing in combination with the washing step of. In the washing step, when washing with a chemical such as acid or alkali, the remaining chemical may be removed by washing with water or hot water after the washing.

[First Washing Step] Various washing methods such as washing with water, washing with hot water, washing with acid,
Alkali cleaning (for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal carbonates such as sodium carbonate, alkali metal hydrogen carbonates such as sodium hydrogen carbonate), solvent cleaning (for example, ester, ketone) , Ether, hydrocarbons, etc.), or a combination thereof. In a preferred step, washing treatment is performed by washing with hot water or washing with acid. In washing with hot water, the temperature of the hot water is, for example, 30 to 100.
C, preferably 50-100 C, more preferably 75.
Approximately 100 ° C, and in order to improve cleaning efficiency, 8
It is often about 5 to 100 ° C. Further, instead of washing with hot water, steam washing, for example, a washing treatment using steam at about 90 to 130 ° C. may be performed.

The acid washing is carried out by using an organic acid (for example, acetic acid, trichloroacetic acid, trifluoroacetic acid, propionic acid, formic acid, citric acid, tartaric acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, etc.). , Inorganic acids (eg hydrofluoric acid, hydrochloric acid, hydrobromic acid and other hydrohalic acids, sulfuric acid, nitric acid, phosphoric acid, etc.)
Can be done using. These acids can be used alone or in combination of two or more. Preferred acids include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. The concentration of the acid can be selected according to the type of the acid as long as it does not adversely affect the plating film or the base material and does not impair the workability, and is, for example, 0.1 to 50% by weight, preferably 1 to 40%.
It is often used as an aqueous solution of about 5% by weight, more preferably about 5 to 30% by weight.

The cleaning liquid may contain a surfactant or the like in order to enhance cleaning efficiency. The cleaning method is not particularly limited, and for example, the plated product (work) may be immersed in the cleaning liquid, the cleaning liquid or the work may be shaken, or the work may be cleaned with the cleaning liquid while irradiating ultrasonic waves. Also,
To increase the cleaning efficiency, heat the cleaning liquid (for example, 30 ~
It may be washed by heating to 80 ° C., preferably about 30 to 60 ° C.). The washing time can be selected according to the type of washing liquid and the washing method, and is, for example, 10 seconds to 120 minutes, preferably about 30 seconds to 60 minutes. In addition, when washing with hot water,
It may be 1 to 90 minutes, preferably 5 to 60 minutes, and may be 10 seconds to 30 minutes, preferably 30 seconds to 20 minutes in the case of acid cleaning.

[Heat Treatment Step] The heat treatment after the cleaning treatment is, for example, baking, induction heating (for example, high frequency heating).
Various heating methods can be adopted, and the type thereof is not particularly limited. Preferred heat treatments include baking treatments and induction heat treatments. When the cleaning after the plating treatment or the cleaning after the heat treatment is adopted, not only when the heating temperature in the heat treatment step is high, but also when the heating temperature is not so high,
Corrosion resistance can be greatly improved. Therefore, the method of the present invention has an advantage that thermal energy can be largely saved and there is no risk of softening due to tempering of the iron-based substrate. The heating temperature is in a wide temperature range, for example, 100 ° C. or higher (for example,
100-600 ° C), preferably 100-500 ° C, more preferably 100-300 ° C, especially 120-250.
The temperature can be appropriately selected from the range of about 0 ° C, and high corrosion resistance can be imparted even at about 150 to 200 ° C. Heating temperature is 10
If the temperature is lower than 0 ° C, it takes a long time to improve the corrosion resistance, and if the treatment is carried out at a high temperature, the workability tends to deteriorate.

The heating temperature can be selected according to the heating method. For example, in the case of a baking process, the heat transfer efficiency is low, and when it is heated at a high temperature, the heat energy loss tends to increase. Therefore, the baking temperature is usually 1
The temperature can be selected within the range of about 00 to 400 ° C, preferably 100 to 300 ° C, more preferably 120 to 250 ° C.
The heat treatment is often performed at a baking temperature of about 150 to 250 ° C. The baking time depends on the baking temperature.
For example, 30 minutes to 12 hours, preferably 1 to 10 hours,
More preferably, it can be selected within a range of about 2 to 8 hours.
Baking can be performed using various heating furnaces such as an infrared heating furnace, a hot air furnace, and an electric furnace.

On the other hand, in the case of induction heating, the iron-based base material such as the cylinder rod can be efficiently heat-treated within a short time, so that the productivity of the corrosion-resistant iron-based member can be remarkably improved. In particular, high frequency heating has high heat treatment efficiency.
In the case of high frequency heating, the heating temperature is 100 to 600 ° C, preferably 120 to 500 ° C, more preferably 150 to 600 ° C.
It can be appropriately selected within the range of about 400 ° C. In the case of high frequency heating, it is difficult to directly measure the heating temperature, but the surface temperature of the iron-based base material can be used as the heating temperature. The degree of heating by the high frequency heating can be arbitrarily controlled by adjusting, for example, the inner diameter of the coil, the width of the coil, the output of the high frequency generator, the frequency, and the relative feed speed between the iron-based base material and the coil. Since these factors are related to each other, it is not possible to independently determine only one factor in heat treatment.

Hereinafter, the outer diameter of the iron-based base material is 30 to 100 m.
When using a rod of mφ, an example of high frequency heating conditions is
This will be described more specifically. As the distance between the coil and the cylinder rod increases, the induced current decreases and the rise in the surface temperature is suppressed. Therefore, the distance between the coil and the cylinder rod is, for example, 10 depending on the degree of heat treatment.
It can be selected in the range of about 50 mm, preferably about 15 to 30 mm. The width of the coil is also related to the heat treatment time and the relative feed rate between the cylinder rod and the coil. When the coil length is short or the feed speed is high, the degree of heat generation is small. Therefore, the length of the coil can be appropriately selected in relation to the feed rate, but it is usually 1
About 0 to 50 mm is sufficient. The relative feed speed between the cylinder rod and the coil is, for example, 0.1 to 5
m / min, preferably about 0.5 to 5 m / min. Since the feeding speed can be increased by the high frequency heating as compared with the baking treatment, the cylinder rod excellent in corrosion resistance can be continuously and efficiently manufactured within a short time.

Since the output of the high frequency generator is proportional to the energy of the induced current, the higher the output, the higher the surface temperature of the cylinder rod. The output of the high frequency generator can be selected within a range of, for example, about 30 to 150 kw. When the frequency becomes smaller, the induced current flows to the deep part of the cylinder rod, and it seems that the local temperature rise is suppressed. The frequency is, for example, 3 kHz to 1 MHz, preferably 4 to 100 kHz, more preferably 4 to 10 kHz.
You can select within a range.

In the case of heat treatment by induction heating, the above conditions can be appropriately selected depending on the size of the iron-based base material such as the cylinder rod and the desired degree of heat treatment. When the iron-based substrate is hardened steel, the heat treatment is preferably performed at a temperature that does not exceed the tempering temperature of the iron-based substrate. After the heat treatment, the plated product is usually gradually cooled.

The heating time in the present invention is significantly shorter than the baking time described in the prior art document. Moreover, in the present invention, the corrosion resistance is remarkably improved by one heat treatment. Furthermore, by combining the heat treatment step of baking (hardening) the hard chrome plating layer and then the heat treatment (baking), the washing step after the heat treatment, and the resin impregnation step, the iron-based base material is no different from stainless steel. Corrosion resistance can be imparted for a long period of time, and the corrosion resistance can be remarkably improved.

[Second Cleaning Step] The cleaning after the heat treatment may be any of washing with water, washing with hot water, acid washing, alkali washing, solvent washing, and a combination of these, as in the case of the first washing step. May be. In a preferred cleaning step, cleaning treatment is carried out by acid cleaning. The acid washing is performed using the same organic acid as that used in the first washing step (for example, acetic acid, trichloroacetic acid, trifluoroacetic acid, propionic acid, formic acid, citric acid, tartaric acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p -Toluenesulfonic acid, etc.) and inorganic acids (for example, hydrofluoric acid, hydrochloric acid, hydrobromic acid and other hydrohalic acids, sulfuric acid, nitric acid, phosphoric acid, etc.). These acids can be used alone or in combination of two or more. Preferred acids include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. The pH of the cleaning solution and the acid concentration of the cleaning solution in the acid cleaning are the same as those in the first cleaning step.

As in the above case, the cleaning solution may contain a surfactant or the like in order to enhance the cleaning efficiency, and the cleaning method can be performed in the same manner as in the first cleaning step.
The washing time can be selected according to the type of washing liquid and the washing method, and is, for example, 10 seconds to 120 minutes, preferably 30 seconds to 6
About 0 minutes, when using a cleaning solution containing an inorganic acid, 1
It may be 0 seconds to 30 minutes, preferably about 30 seconds to 20 minutes. After washing with a chemical such as an acid, if necessary, further washing with water or hot water may be performed to remove the remaining chemical.

In the first cleaning step and the second cleaning step, the plating treatment step may be followed by hot water washing or acid washing, and after the heat treatment step, hot water washing may be performed. By performing acid cleaning after at least one of the steps, especially the heat treatment step, high corrosion resistance can be imparted to the chromium plated product with good reproducibility.

[Resin Impregnation Step] In the resin impregnation (sealing) step, if a resin or a sealing agent is impregnated, many cracks or pinholes in the hard chrome plating layer will be buried and sealed. The corrosion resistance of the iron-based base material is significantly improved.
The resin or sealant used as the impregnating agent in the impregnation treatment may be any resin that can impart corrosion resistance, and examples thereof include polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate. Thermoplastic resin such as copolymer, polyvinyl acetal, acrylic resin, styrene polymer, polyester, polyamide, silicone resin; thermosetting acrylic resin, epoxy resin, urethane resin, phenol resin, vinyl ester resin, unsaturated polyester, diallyl Examples thereof include phthalate resin, thermosetting silicone resin, polyimide, melamine resin, urea resin and the like. The thermosetting resin or the sealing agent may contain a curing agent or a cross-linking agent depending on the type of resin.

The preferred resin or sealant includes a resin having high corrosion resistance, for example, a thermosetting resin such as a thermosetting acrylic resin. Further, a preferable thermosetting acrylic resin can be composed of an acrylic or methacrylic oligomer and / or an acrylic or methacrylic monomer.
Examples of (meth) acrylic oligomers and monomers include polyfunctional oligomers having two or more (meth) acryloyl groups (eg, epoxy acrylate, oligoester acrylate, urethane acrylate, and methacrylates corresponding to these), and 2 or more. (Meta)
Polyfunctional monomer having an acryloyl group (for example, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol Diacrylate, tetramethylene glycol diacrylate, hexanediol diacrylate, neopentyl glycol diacrylate, 2,2-bis (4-acryloyloxyethoxyphenyl) propane, 2,2-bis (4-acryloyloxydiethoxyphenyl) propane , Trimethylolpropane triacrylate, pentaerythritol tetraacrylate And the like corresponding methacrylates to), monofunctional (meth) acrylate (e.g., methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, phenyl acrylate, benzyl acrylate and the corresponding methacrylates thereto) are included.
These compounds can be used alone or in combination of two or more.

A liquid resin or a sealant (oligomer), particularly a non-volatile liquid resin or a sealant is preferable in order to enhance the impregnation efficiency into the hard chromium plating layer. The resin and sealant may be used as a solution or dispersion, especially as an aqueous solution or an organic solvent solution. As the solvent, depending on the type of the resin, for example, water, aliphatic or alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, esters, ketones, ethers, etc. Organic solvents and mixed solvents thereof can be used. The content of the non-volatile resin or the sealing agent in the impregnating agent is, for example, 0.1 to 100% by weight, preferably 10 to 100% by weight, and more preferably 50 to 100% by weight. The viscosity of the resin as the impregnating agent or the encapsulant can be selected within a range that does not adversely affect the impregnating property, and is, for example, about 1 to 50 cp at 25 ° C.
s, preferably 1 to 30 cps, more preferably 1 to
It is about 15 cps. The resin may contain additives such as a stabilizer, an antiaging agent, and a colorant, if necessary.

The resin impregnation may be carried out by a conventional method, for example, a dipping method under normal pressure. However, in order to efficiently impregnate the resin, it is preferable to impregnate under reduced pressure or pressure. Impregnation is usually performed at least under reduced pressure. It is also preferable that the iron-based base material is subjected to degassing under reduced pressure prior to the impregnation treatment and then subjected to the impregnation treatment. These resin impregnation methods can be performed in combination.

The impregnation of the resin under reduced pressure includes (1) a vacuum impregnation method in which the inside of a predetermined container containing the chromium-plated product and the resin or sealing agent (preferably liquid resin or sealing agent) is reduced in pressure;
(2) Vacuum dip impregnation method in which the inside of the container containing the chrome-plated product is decompressed and degassed, and the resin or sealing agent is fed into the container to impregnate the resin; (3) The chrome-plated product is housed The inside of the container is depressurized and degassed, and the resin or sealant is fed into the container to impregnate the resin under reduced pressure, and the inside of the container is further pressurized to impregnate the resin or sealant. be able to. The degree of pressure reduction during impregnation can be appropriately selected and is, for example, 0.1 to 100 Torr, preferably 1 to 50.
Torr, more preferably about 1 to 20 Torr. The impregnation time is usually 30 seconds to 1 hour, preferably 1
It is about 30 minutes. Prior to the impregnation, it is preferable that the resin or the sealant is degassed under a reduced pressure equal to or less than the reduced pressure in the resin impregnation step to prevent the formation of bubbles. After the impregnation is completed under the reduced pressure, the container is opened to the atmospheric pressure.
Often it is preferable to do it gradually.

The resin is impregnated under pressure, for example, a pressure of 1 to 20 kg / cm ² , preferably ^{2 to} 10 kg / cm depending on the thickness of the chromium plating layer and the chromium plating conditions.
^The impregnation time is the same as above.

The resin impregnation may be carried out at room temperature, for example, under heating at about 30 to 70 ° C. When a thermosetting resin or a sealant is used, the impregnation temperature is often lower than the curing temperature of the thermosetting resin or the sealant.

The resin or sealant may be impregnated at least once, but may be impregnated multiple times. The preferred number of times the resin is impregnated is about 1 to 3. The number of times of impregnation is the number of times that a series of impregnation steps are performed once.
That is, when the resin is impregnated by combining vacuum impregnation and pressure impregnation, the impregnation steps of vacuum impregnation and pressure impregnation are performed once.

The present invention is characterized in that high corrosion resistance can be imparted even when the impregnated amount of resin or sealant is extremely small. The amount of resin or sealant impregnated varies depending on the number of cracks in the hard chrome plating layer, the depth of the cracks, etc., but is usually 1000 mg per 100 g of the hard chrome plating layer.
The following (1% by weight or less), for example, 1 to 100 mg (0.
001 to 0.1% by weight). The impregnation rate is
It can be evaluated by the weight increase due to resin impregnation.

After the impregnation treatment, the chrome-plated product may be subjected to a liquid draining process to remove excess resin or sealant. Further, the drained plated product may be subjected to a cleaning step. In this cleaning step, if a good solvent is used for the resin or the sealant, the resin impregnated in the defective portion of the hard chrome plating layer will elute. It is preferable to use a poor solvent. The poor solvent can be selected according to the type of resin or sealant, but usually water or the like can be used. In addition,
Washing with a poor solvent may be carried out while heating or heating, and can be carried out by a physical method utilizing a water flow such as bubbling or jet flow.

[Curing Step] When a thermosetting resin (or thermosetting oligomer) is used as a resin or a sealant, the iron-based substrate is usually subjected to a curing step. The thermosetting resin or the encapsulant may be cured according to the curing temperature of the resin, for example, 5
It can be performed at 0 to 200 ° C, preferably about 80 to 150 ° C. Further, the thermosetting resin or the sealant can be cured using a heating furnace or the like, or in hot water. Curing with hot water can be performed at a temperature of 7
0-100 ° C (preferably 85-100 ° C, especially 95-
It can be carried out by immersing the impregnated plated product (workpiece) in hot water of about 100 ° C. for about 5 to 60 minutes (preferably 10 to 30 minutes). The hardening with hot water may be carried out in one step, but it may be advantageous to improve the corrosion resistance by hardening in a plurality of steps in which hot water having a successively higher temperature is used for hardening. For example, rather than curing with hot water of about 70 ° C. or hot water of about 100 ° C. alone,
After the hardening treatment with hot water of about 70 ° C. and the hardening treatment with hot water of about 100 ° C., high corrosion resistance can be imparted.
When cured by using hot water, anaerobic thermosetting resin (particularly (meth) acrylic oligomer and monomer)
Even then, it can be cured smoothly.

The impregnation step and the curing step may be repeated a plurality of times to impregnate the cracks in the hard chrome plating layer with a resin for sealing.

[Finishing Step] After the resin impregnation treatment, the hard chrome plating layer of the plated product is preferably subjected to a buffing step. By subjecting the hard chrome plated product to the buffing process, the corrosion resistance can be further enhanced. This buffing can be performed in the same manner as the polishing step. A preferable method is a method in which a large polishing force is applied to perform polishing, and fine buffing is sequentially performed. Especially after performing ring buffing of about # 400-1000,
It is preferable to perform cotton buffing or sisal buffing with an abrasive of about # 240 to 600, and then it is also preferable to perform open sisal buffing. When buffing is performed by such a method, a large polishing force acts on the ring buff, and the cotton buff or sisal buff not only cuts the protrusions of the plating layer, but also plastically deforms the plating layer. Since the openings such as cracks are closed and smoothed, the corrosion resistance is improved.

[Repeat Treatment] In the method for producing a corrosion-resistant iron-based member through the cycle including the plating treatment step, the first cleaning step, the heat treatment step, the second cleaning step, the impregnation step, and the finishing step. By the above-mentioned one cycle, extremely high corrosion resistance can be imparted, and the iron-based member is hardly corroded. In the above cycle,
At least one of the first cleaning step and the second cleaning step, particularly the second cleaning step, is adopted. In the above cycle, the impregnation step or the impregnation and curing step may be repeated at least twice. Further, by repeating the cycle including the plating treatment step, the first cleaning step, the heat treatment step, the second cleaning step, the impregnation step, and the finishing step at least twice, extremely high corrosion resistance. May be applied to the iron-based member.
The number of repetitions of the cycle may be 2 or more,
Usually, it is often about 2 to 3 times. When performing hard chrome plating a plurality of times, the thickness of the hard chrome plated layer by each plating treatment can be appropriately selected from the above range of 10 to 200 μm according to the number of times of plating, for example, 10 to
The thickness is 100 μm, preferably about 15 to 50 μm. When performing hard chrome plating a plurality of times, it is usually difficult to form a uniform hard chrome plated layer with the impregnated resin when the hard chrome plating treatment is performed after impregnating the resin. However, in the above-mentioned cycle, since the buffing is performed after the resin impregnation step, a uniform hard chrome plating layer can usually be formed even if the hard chrome plating treatment is performed a plurality of times.

[Characteristics of Corrosion-Resistant Iron-Based Member] The final thickness of the hard chromium plating layer thus formed is, for example, 5 to 100 μm, preferably 10 to 80 μm, and more preferably 15 to 75 μm. is there. Particularly preferable thickness of the hard chrome plating layer in the final product is 10 to 10.
It is about 50 μm (for example, 20 to 50 μm). The obtained iron-based member such as a cylinder rod does not corrode even if the plating layer has cracks or the like even under severe conditions, for example, when subjected to a salt spray test.

For example, JIS H 8502 (198)
Even if the Cass test specified in 8) is performed for 96 hours, the rating number as an index of the corroded area is 9.5 to 1
0.0, preferably about 9.8 to 10.0, particularly 10.
It is about 0 and hardly corrodes. In addition, JIS H 8
Even after conducting the salt spray test defined in 502 for 1200 hours, the rating number is 9.5 to 10.0, preferably about 9.8 to 10.0, and particularly about 10.0.
It hardly corrodes.

According to the method of the present invention, high corrosion resistance can be imparted to the corrosive iron-based substrate. Therefore, the present invention is
It can be applied to various corrosive iron-based base materials, for example, iron-based members used in a corrosive environment or an environment in which corrosion is promoted, particularly sliding members whose corrosion resistance is likely to decrease due to sliding contact or the like. Especially, it can be suitably applied to various cylinder rods, for example, cylinder rods for construction machines, particularly piston rods.

[Cylinder Rod] In order to control the forward / backward movement of the rod, the cylinder rod is provided with position detecting concave portions in the axial direction of the cylindrical rod, for example, concave portions scattered in the axial direction of the rod, preferably at a predetermined pitch. A plurality of grooves extending in the direction may be formed. In such a cylinder rod, the positions of a plurality of grooves formed in the circumferential direction are determined by a position detection sensor (for example, an electromagnetic position detection sensor that detects a change in magnetic resistance, a sensor such as a potentiometer that detects a capacitance). Can be detected by A preferable sensor includes an electromagnetic position detection sensor that can detect the thickness (depth) and width of the groove by magnetic means by utilizing the fact that eddy current flows corresponding to the groove. Therefore, when the rod is used as the piston rod of the cylinder,
By counting the detection signal of the eddy current generated in response to the advance / retreat of the piston rod with respect to the cylinder, the advance / retreat degree of the piston rod can be detected.

The position detecting recess is preferably an annular groove or a spiral groove formed over the entire circumferential surface of the rod, or a groove extending at least partially in the circumferential direction along the axial direction of the rod.
Particularly preferable position detecting grooves extend in a region extending in the axial direction of the rod in the circumferential direction orthogonal to the axial direction of the rod. The pitch of the grooves can be selected within a range in which the position detection accuracy of the grooves does not decrease, and is, for example, 0.1 to 50 mm, preferably 0.5 to 25 mm. The depth of the groove can be appropriately selected within a range in which the workability of the groove is not deteriorated.
The thickness is 1 to 200 μm, preferably 10 to 150 μm, and more preferably 25 to 100 μm. The groove of the rod may include a reference groove serving as a reference marker. The cylinder rod including the reference marker is formed in the axial direction of the cylindrical iron-based rod with a plurality of position detecting grooves extending in the circumferential direction at a predetermined pitch and in the circumferential direction at a pitch larger than the pitch of these grooves. And a reference groove.

In such a rod, the reference groove is used as a reference marker, and a detection signal from a position detection sensor for detecting the reference groove is used as a reference signal, and based on this reference signal, the rod is moved forward or backward from the cylinder. Can be made. When the rod having the reference groove is used, the detection signal of the eddy current generated in the reference groove can be used as the reference signal.Therefore, it is necessary to return the rod into the cylinder once to the reference point and then move the rod forward or backward. Therefore, the stroke for returning the rod to the reference position can be reduced. Moreover, the rod can be moved forward or backward by a predetermined stroke while counting the detection signal of the eddy current generated in the position detection groove with reference to the reference signal.

The reference groove is not limited to the groove shape and can be formed in the same manner as the position detecting recess. Similar to the above, the preferable reference recess is a groove that extends at least partially in the circumferential direction along the axial direction of the rod. A particularly preferred reference groove is
The region extending in the axial direction of the rod extends in the circumferential direction orthogonal to the axial direction of the rod.

In such a cylinder rod, the position detecting recess and the reference recess are filled with the hard chrome plating layer, and the surface of the rod is covered with a hard chrome plating layer having a smooth surface. .

The cylinder rod can be manufactured by forming a plurality of recesses in the axial direction of the iron-based rod and then forming a hard chromium plating layer in the same manner as described above. The concave portion of the cylinder rod can be formed by screen-printing method, photoresist method, tape masking method or the like to form a resist by leaving a portion corresponding to the concave portion, and then etching. Further, when forming the hard chrome plating layer, it is preferable to mask the region of the rod excluding the concave portion to perform the hard chrome plating, remove the mask, and perform the hard chrome plating again. In this case, after each hard chrome plating, the resin impregnation and heat treatment may be appropriately combined with buffing if necessary, and after the second hard chrome plating treatment, finally, The resin impregnation, heat treatment, and buffing, if necessary, may be combined. Even after the mask is removed, even if the chromium-plated portion and iron of the iron-based rod coexist, in order to efficiently etch the surface of the iron-based rod, an etching solution, preferably ferric chloride, is used in advance. It is preferable to adjust the base by etching using an etching solution containing. In addition,
By performing the etching treatment by anodic oxidation, the surface of the chromium plated portion is also etched, and the entire surface of the iron-based rod can be cleaned and activated.

[0057]

According to the method of the present invention, since the hard chrome plating, the heat treatment, the washing treatment and the resin impregnation are combined, the corrosion-resistant iron which is remarkably excellent in the corrosion resistance even if the thickness of the hard chrome plating layer is small. The system member can be reliably obtained. Further, the corrosion-resistant iron-based member can be surely provided with corrosion resistance equal to or higher than that of stainless steel, and the corrosion-resistant iron-based member can be manufactured with a high yield. Further, the cylinder rod having the above-mentioned excellent properties can be manufactured economically and with high productivity.

[0058]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 A rod made of low carbon steel (S43C) having an outer diameter of 25 mmφ was degreased and buffed with # 320 ring buff, # 600 ring buff, # 800 ring buff and sisal buff (base buff treatment). Using the following plating bath, the current density of 35
Etching was performed for 3 minutes at A / dm ² . Plating bath composition Chromic anhydride: 250 g / L Sulfuric acid: 2.5 g / L Trivalent chromium: 1.0 g / L Then, the plating bath temperature was 50 ° C. and the current density was 35 A /
The rod was chromium-plated under conditions of dm ² and plating time of 100 minutes to form a hard chromium-plated layer having a thickness of 35 μm.

The obtained hard chrome plated product is heated to 100 ° C.
Rinse with hot water for 40 minutes, bake at a temperature of 250 ° C for 6 hours, and slowly cool, then wash with sulfuric acid (sulfuric acid concentration 15 g /
It wash | cleaned for 1 minute with L), and used for the resin impregnation process.

In this resin impregnation step, an impregnating solution containing an acrylic resin-based impregnating agent (DIAKITE PF-1900, manufactured by Diafloc Co., Ltd.) and a curing agent (A-1, manufactured by Diafloc Co., Ltd.) was used. I did. That is, the inside of the vacuum container accommodating the hard chrome plated rod is
Degas with Torr for 10 minutes, send the impregnating liquid into the container,
After vacuum immersion for 10 minutes at 5 Torr, it was opened under atmospheric pressure. Then, the rod was taken out, excess impregnating liquid was drained off, placed in a drying oven and heated at 175 ° C. for 2 hours to cure the resin, and a hard chrome plated rod impregnated with the resin was obtained.

After the rod was gradually cooled, it was subjected to a finishing buffing process to produce a hard chromium plated piston rod. The finishing buffs were performed in the order of # 800 ring buff and sisal buff. The thickness of the hard chrome plating layer was 30 μm by buffing.

Example 2 In the second washing step, a sulfuric acid washing solution (sulfuric acid concentration: 15 g /
L) except for washing for 10 minutes, in the same manner as in Example 1,
Got a piston rod.

Example 3 A piston rod was obtained in the same manner as in Example 1 except that in the second washing step, the aqueous solution of sulfuric acid I was replaced with an aqueous solution of hydrochloric acid (hydrochloric acid concentration of 15 g / L) for 10 minutes.

Example 4 A rod made of low carbon steel (S43C) having an outer diameter of 25 mmφ was degreased, the same plating bath as in Example 1 was used, and the rod was used as an anode, and the current density was 35 A / dm ² , by anodization.
Etching was performed for 3 minutes. Then, in the same manner as in Example 1, the rod was plated with chrome to form a hard chrome plated layer having a thickness of 35 μm. The obtained hard chrome-plated product is washed with hot water at 100 ° C for 40 minutes to obtain a temperature of 175
After baking at 6 ° C for 6 hours and slow cooling, it was washed with a sulfuric acid cleaning solution (sulfuric acid concentration 15 g / L) for 1 minute, and subjected to the same resin impregnation step, curing step and finishing buff step as in Example 1 to obtain hard chromium plating. The applied piston rod was produced.

Example 5 A sulfuric acid cleaning solution (sulfuric acid concentration 15 g /
L) was washed for 10 minutes in the same manner as in Example 6,
Got a piston rod.

Examples 6 to 8 The first washing step was carried out under the following conditions, and the acid washing solution (sulfuric acid concentration: 15 g / L) was used in the second washing step.
A piston rod was obtained in the same manner as in Example 4 except that cleaning was performed for 0 minutes.

First Washing Step Example 6: Rinse with hot water at 100 ° C. for 10 minutes Example 7: Rinse with hot water at 90 ° C. for 10 minutes Example 8: None Example 9 Outer diameter 25 mmφ low carbon A steel (S43C) rod was degreased, subjected to a base buffing treatment in the same manner as in Example 1, and used the same plating bath as in Example 1, using the rod as an anode to obtain a current density of 35 A / dm ² , Etching was performed for 3 minutes. Then, in the same manner as in Example 1, the rod was plated with chrome to form a hard chrome plated layer having a thickness of 35 μm. The obtained hard chrome plated product is 90 ℃
Of hot water for 40 minutes, baked at a temperature of 250 ° C. for 4 hours and 30 minutes, gradually cooled, and then subjected to the same resin impregnation step, curing step and finishing buff step as in Example 1 without acid washing. A piston rod plated with hard chrome was prepared.

Example 10 A piston rod was obtained in the same manner as in Example 1 except that baking was performed at 150 ° C. for 6 hours, and a hard chrome plating layer having a thickness of 25 μm was formed by a finishing buffing process.

Example 11 Instead of the rod of Example 1, a rod made of low carbon steel (S43C) having an outer diameter of 65 mmφ (entire rod length 590 m
m, shaft length 120 mm) and in the same manner as in Example 1 to form a hard chrome plating layer having a thickness of 30 μm. Then, the chrome-plated product was washed with hot water in the same manner as in Example 2, and in the heat treatment step, the coil (inner diameter 86 mmφ,
The rod is placed in the hollow part with a width of 20 mm), and the voltage is 300
V, output of high frequency generator 50kw, frequency 5.0kH
Induction heat treatment was carried out under the conditions of z and coil feed rate of 2.8 m / min, and cleaning was performed with an acid cleaning solution as in Example 2. The surface temperature of the piston rod in the heat treatment step was measured and found to be 220 ° C. The rod washed with the acid washing liquid was subjected to the resin impregnation step in the same manner as in Example 1, impregnated with the resin, and then subjected to the final buffing to produce a cylinder rod having a hard chromium plating layer of 27 μm in thickness.

Example 12 Using the coil of Example 11, high-frequency heating conditions were set to voltage 4
60V, high frequency generator output 80kw, frequency 6.0k
A cylinder rod was produced in the same manner as in Example 11 except that the feed rate was Hz and the coil feed rate was 3.3 m / min. The surface temperature of the piston rod when subjected to the induction heat treatment under the above conditions was 500 ° C.

Comparative Example 1 A thickness of 30 μm was obtained in the same manner as in Example 1 without performing the first cleaning treatment, the baking treatment and the second cleaning treatment.
A piston rod having a hard chrome plated layer of was obtained.

Comparative Example 2 A piston rod having a hard chromium plating layer with a thickness of 30 μm was obtained in the same manner as in Example 1 without performing the first cleaning treatment, the second cleaning treatment and the resin impregnation treatment. .

Comparative Example 3 A piston rod having a hard chromium plating layer with a thickness of 30 μm formed in the same manner as in Example 1 without performing the first cleaning treatment, baking treatment, second cleaning treatment and resin impregnation treatment. Got

Comparative Example 4 Chromium plating was performed in the same manner as in Example 1 without performing the first cleaning treatment and the second cleaning treatment, and the thickness was 50 μm.
m hard chrome plated layer was formed.

The piston rods obtained in the respective examples and comparative examples were subjected to the Cass test method defined in JIS H8502 (1988), and the rods were subjected to the spraying time (96 hours and 480 hours). The degree of corrosion defects (corrosion resistance) was evaluated by a rating number standard chart without wiping the rod surface. The test solution in the Cass test was obtained by dissolving 0.268 g of cupric chloride dihydrate in an aqueous solution having a sodium chloride concentration of 40 g / L and adjusting the pH to 3.0 with acetic acid.
The Cass test was performed at 50 ° C. The results are shown in Table 1. The rating number standard chart corresponds to the total corrosion area ratio (%), and the relationship between the total corrosion area and the rating number is as follows: the larger the value, the higher the corrosion resistance. Total corrosion area (%) Rating number 0 10 0 to 0.02 9.8 0.02 to 0.05 9.5 0.05 to 0.07 9.3 0.07 to 0.10 9.0 0.0. 10 to 0.25 8 0.25 to 0.50 7 0.50 to 1.00 6 1.00 to 2.50 5 2.50 to 5.00 4 5.00 to 10.0 3 10.0 to 25.0 2 25.0-50.0 1

[0076]

[Table 1] As shown in Table 1, the piston rods of the respective examples have significantly improved corrosion resistance as compared with the rods of the comparative examples, and hardly corrode.

Examples 13 to 15 The operations of Example 2, Example 5 and Example 8 were repeated at different dates and times to obtain a total of 20 piston rods at a rate of 1 rod per day.

Comparative Examples 5 and 6 The operations of Example 2 and Example 5 were repeated at different dates without performing the cleaning treatment in the first cleaning step and the second cleaning step. In total, a total of 20 piston rods were obtained.

Then, a cast test was conducted in the same manner as described above, and the degree of corrosion defects (corrosion resistance) at a spraying time of 480 hours was evaluated by a rating number standard chart. When the number of rods was classified according to the level of corrosion resistance (rating number), the results shown in Table 2 were obtained.

[0080]

[Table 2] As is clear from Table 2, by adopting the cleaning step, high corrosion resistance can be surely imparted to the chromium plated product even if the heat treatment temperature is low.

Claims (12)

[Claims] 1. A method comprising a plating treatment step of plating a corrosive iron-based substrate with hard chromium, a heat treatment step of heat treatment, an impregnation step of impregnating a resin or a sealing agent, and a buffing finishing step. A method for manufacturing a corrosion-resistant iron-based member, which comprises performing a cleaning process after the plating process and / or the heat treatment process. 2. A method of cleaning with an acid after the heat treatment step.
A method for producing the corrosion-resistant iron-based member as described. 3. The method for producing a corrosion-resistant iron-based member according to claim 1, further comprising washing with an inorganic acid after the heat treatment step. 4. A plating treatment step of plating a corrosive iron-based cylindrical rod with hard chrome to form a hard chrome plating layer of 10 to 100 μm, a heat treatment step of heat treatment at a temperature of 100 ° C. or higher, and at least under reduced pressure. A method comprising an impregnation step of impregnating a thermosetting resin or a sealing agent, a curing step of curing the impregnated resin or sealing agent, and a finishing step of buffing, at least after a heat treatment step, with an acid. The method for producing a corrosion-resistant iron-based member according to claim 1, wherein the method is cleaning. 5. A temperature of 100 to 500 in the heat treatment process.
The method for producing a corrosion-resistant iron-based member according to claim 1, wherein the heat treatment is performed at ℃. 6. The method for producing a corrosion-resistant iron-based member according to claim 1, wherein the iron-based base material is a cylinder rod. 7. A temperature of 100 to 300 in the heat treatment process.
The method for producing a corrosion-resistant iron-based member according to claim 1, wherein the heat treatment is performed at 30 ° C. for 12 minutes. 8. An acrylic or methacrylic oligomer or monomer having a viscosity at 25 ° C. of 1 to 50 c.
5. A ps thermosetting resin or a sealant is used.
A method for producing the corrosion-resistant member as described above. 9. The method for producing a corrosion-resistant iron-based member according to claim 1, wherein the impregnation is performed under a reduced pressure of 0.1 to 100 Torr. 10. The method for producing a corrosion-resistant iron-based member according to claim 1, wherein a hard chromium plating layer having a thickness of 5 to 95 μm is formed by buffing. 11. An iron-based base material is hard-chrome plated to 15
A plating treatment step of forming a hard chrome plating layer of -60 μm, and a heat treatment step of heat treatment at 120 to 250 ° C.
A washing step of washing with an inorganic acid, an impregnation step of impregnating a thermosetting resin or a sealing agent having a viscosity of 1 to 15 cps at 25 ° C. under a reduced pressure of 1 to 50 Torr, and curing the impregnated resin or the sealing agent. A method for producing a corrosive iron-based base material, which comprises a curing step for performing buffing and a finishing step for buffing. 12. A corrosive iron-based cylindrical rod is hard-chrome plated, the plated rod is heat-treated, the heat-treated rod is impregnated with a thermosetting resin or a sealant, and the impregnated rod is buffed. A corrosion-resistant iron-based member obtained by performing a cleaning process after the plating process and / or the heat treatment, including JIS H8502
A corrosion-resistant iron-based member having a rating number of 9.5 to 10.0 when subjected to a cast test for 96 hours.