JPS58500253A - High speed chrome alloy plating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] High speed chromium alloy plating The widespread use of relatively rare materials, e.g. nickel and chromium, makes it possible to Corrosion resistance of the support, for example steel or brass, for example 25 μm chromium alloy It may be reduced by a permissive lubrication method that can form a transparent film. chromium Shiny decorative coatings of alloys are also valuable in certain applications.

In the past, most commercial plating of bright chrome was based on hexavalent chromium, e.g. It was carried out from a solution of romic acid.

Disadvantageously, these baths are complexed when chromium is anionic , has historically been ineffective for plating alloys. Divalent chromium and/or When attempting to perform plating from a solution of hexavalent chromium, some alloy plating may occur. However, the deposition rate is low and the current density is about 1 A/1n2 (15 A/d m2) typically lower, often very low.

Moreover, when electrodepositing alloys from solutions containing metal ions, more active metals It is well known that less active metals will preferentially precipitate.

Considering chromium alloys containing iron and/or nickel, nickel, iron and The relative redox potential of nickel and chromium is such that nickel- and iron-rich precipitates form. would be expected. Chromium is clearly more active and 58500253 (2) The potential for the reduction of Cr to Cr is approximately -0.74 volts.

The object of the present invention is to combine iron and, if necessary, nickel and/or cobalt. An object of the present invention is to provide a method for plating chromium alloy.

Furthermore, the object of the present invention is to improve The plating of such alloy compositions is substantially modern in comparison.

It is also an object of the present invention to provide a method for plating chromium alloys at high speed. be.

Furthermore, the object of the present invention is to extract chromium from a solution consisting of divalent chromium and trivalent chromium. It is an object of the present invention to provide such an electrodeposition method for producing an alloy.

Finally, it is an object of the present invention to control the formation of thick, dense ROM alloy precipitates. The objective is to provide such a method that can be used to

In accordance with these objectives, the present invention provides ions of divalent chromium and divalent chromium, iron ions and optionally additional alloying constituents such as nickel and/or plating chromium alloys at high speed from an electrolytic solution containing cobalt ions. This is a method to High speed plating requires less than 75 A/d (preferably less than At a current density of at least about 15 OA/dm), at a pH of about 0.5 - 2 o, the cathode moving the solution at a rate of at least about 1 m/sec (preferably 1-8 m/sec). Implement while doing so.

5-80% (by weight) chromium, 20-95% iron and 0-50% nickel. The composition of the precipitate is preferably 2097e or saturated divalent/trivalent chromium, mono- to Electrolysis with metal ion concentrations of iron of 50971 and nickel of 0 to 509/l Formed by electrolyzing a solution. acid, sulfamic acid, hydrochloric acid, phosphoric acid It is preferred that complex anions of and boric acid are present in the electrolyte.

When using an insoluble anode, a barrier is typically placed around the cathode to protect it. If the anode oxidizes otherwise divalent/hexavalent chromium to the hexavalent state, anodization Prevents migration of reaction products to the cathode.

Within the general conditions described above, the best deposition of chromium alloys is achieved when the free acid in the electrolyte is approximately By strictly maintaining the pH within a narrow range corresponding to a pH of 1.7-1.8, It was also discovered that it is possible to Do not use very accurate weighing for pHO monitoring ( or titration may be required to establish the free amount in the bath. Dew.

The present invention also provides 2097e or saturated divalent/hexavalent chromium ions, 1 to 50 Consisting of iron ions of 9/e and nickel ions of 0 to 5097e in total, pH An inorganic acid consisting of a novel electroplating solution in which the complexing anions can be used in the electrolyte.

Description of the invention The present invention contains iron and, if necessary, nickel and/or cobalt. This is a method of electroplating chromium alloy. The composition of the alloy is preferably 5-80 % chromium, 20-95% iron and 0-50% total nickel and/or falls within the range (weight) of cobalt.

Alloys outside this range can be plated according to the present invention to obtain the desired corrosion resistant coating. This requires at least about 5-10% chromium. more than the preferred range The high chromium and nickel content unfavorably increases the cost of the alloy and therefore , not preferred. Chromium-nickel-iron alloy is a preferred coating composition; In particular, 600 and 400 class stainless steels are preferred.

604 type stainless steel (18%Cr-8%N1-2%Mn-balance F) is one is a desirable composition. However, examples of chromium-iron-nickel alloys and Consideration will be given to cobalt, as it is known in this field, to all of nickel. It is intended to include alloys that can be used in place of or as a part of the alloy. for example , other impurities that can enter the precipitate from the anode can also be precipitated out without harm. . Manganese, silicon and copper are examples.

Alloy coatings can be applied to common cathode surfaces of steel, iron, aluminium, brass or copper, for example. formed on top. Insoluble anodes, such as those made from lead, can be used, but iron or Anodes of soluble alloys of It was for business.

plating solution The electrolyte preferably contains 209/e to saturated chromium ions, 1 to 509/e Iron ions and nickel and/or cobalt ions totaling O~50y/e It is a divalent/diavalent chromium salt solution containing. Hexavalent chromium is converted to divalent form and vice versa, their exact ratio is clearly identified. I didn't.

Therefore, the two species are both believed to exist and are necessary, and the hexavalent References to chromium encompass lower valence species simultaneously present in the bath. I also intend to do that. The excess divalent form reduces the nickel ions to metal and It has a negative effect on nickel precipitation as it tends to form precipitates and plating on surfaces such as nickel. I can beat it.

Some electrolytes require a stabilization period before obtaining a better product. this is It may be necessary to produce a certain minimum amount of divalent chromium in the bath.

Plead anions, commonly used in chromium plating, are also required in the method of the present invention. virtue These include mineral acids: sulfuric acid, electrolyte pH, thick, shiny and semi-glossy coatings. It was found to be a critical factor in depositing the film. Within the pH range of 0.5-20 and has a matte texture, but is still useful in corrosion and wear resistant applications. It is possible to deposit an excellent chromium alloy film. These coatings generally have a thickness of It is limited to about 12-25 μm. Thicker coatings result in increased internal stresses It has a tendency to peel and peel.

However, when the acidity of the electrolyte corresponds to a pH of about 1,7-1,8, the shine Coatings and semi-gloss coatings can be obtained, which coatings have a thickness of more than 125 μm. It has been found that even at low temperatures, the adhesion is dense and free of cracks. child The reasons for this phenomenon are not understood at this point, but the results over this range are dramatic. .

This acidity range is very narrow, so measure it and maintain it throughout the solution. Things can be difficult.

Indeed, sensitive instruments exist to measure pH, and in fact, pH meters can be suitably used. However, for titration against standard base solutions, e.g. Determining acidity by measuring the amount of “7 free acids” is recommended for accuracy. preferred for this purpose. "The content of free acid 1 is determined by p 0.0 required to make H3.5. As the amount of NaOH solution in IN, we Define. The preferred range of free acid used in this titration method is about 0.5 m to 1.5 m. 5 mi of NaOH, which corresponds to a pH of approximately 1.8-1.7, respectively. .

The temperature of the plating solution is preferably in the range of 25-75r.

Implementation conditions Along with acidity, the most important implementation parameters to obtain a crack-free, adherent coating. The meters are current density and agitation or solution flow. Acidity and solution flow are Acidity has a particular effect on the deposition rate and density of the coating, but acidity has a negative effect on the plating reaction between nickel and iron. does not significantly affect the composition of the precipitate, except at very low pH where the reaction reduces efficiency. No effect. The composition is influenced more by the current density and the composition of the electrolyte. receive.

It is well-reasoned that the least active metals precipitate preferentially over the more active metals. It is understood. However, the method of the present invention requires high current density and solution flow. The composition of the precipitate can be determined, especially of iron-chromium from the sulfamate solution. For binary alloys, even for high chromium precipitates, prior art plating methods The composition of the electrolyte can be approximated more closely than that of the electrolytic solution.

The current density for the method of the invention is at least 75 A/dm, but preferably Preferably, it is within the range of about 150 to 400 A/dm2. The higher current density is It is more favorable for the precipitation of chromium than iron or other metals, and is highly soluble from hexavalent chromium solutions. This is necessary to obtain alloys with high chromium content.

At such high currents, chromium, iron and especially nickel or cobalt close adhesion unless associated with high agitation or solution flow rates. It would be difficult to plate with such deposits. The cathode also arises from the flow of the solution. , the turbulent flow near the cathode allows the cation-rich solution to replace the depleted electrolyte. A relative velocity of at least 1 m/s between the cathode surface and the plating solution. motion is generally sufficient to create the necessary turbulent conditions for good precipitation. . Typically, speeds of 1 to 80 m/s can be used, with 1 to 8 m/s being preferred. .

When using agitation and other means of moving the anodic product to the area of the cathode, the insoluble between the anode and the cathode), so that the anode product is divalent near the cathode. It may also be necessary to avoid oxidizing trivalent chromium. normal porous A membrane (ceramic cup) can be used around the cathode for this purpose.

Example 1 - Composition Comparable to the Composition of an Iron-Chromium Alloy Bath According to the invention, chromium and Although the redox potential of the iron plating reaction is different, the metal ratio in the electrolyte and the actual Alloys having qualitatively the same composition ratio can be deposited.

In samples labeled 43F and 52A, iron and chromium sulfamate The electrolyte is prepared by dissolving the metal in an acid solution of sulfamic acid. Ta. Concentrations are 0.25 molar chromium (1':, 9/e cr) and 0.75 molar l/ of iron (42!/e of "e").The current density was 160 A/dm, The rod-shaped copper cathode was then rotated at a surface speed of 25 m/sec. Using a lead anode, It was isolated from the cathode by a porous alumina diaslum. The temperature is about 9 They were 37C and 49r.

Sample 43F used 10 minutes of precipitation at pH 1,6; - Actual sample 52 used p)(i , 7 for 5 minutes. In both cases, the weight ratio of the alloy composition is Qualitatively the same as the electrolyte, 72Fe-28Or and 75Fe, respectively. -25Cr (±3%). Cathode efficiency was about 26-27%.

At the end of the precipitation, the lead anode showed signs of dissolving into the sulfaminate.

To avoid this in longer precipitations, platinum or graphite anodes are used. Alternatively, preferably a soluble anode can be used.

Example 2 - Effect of pH Chromium sulfate (09 mol), iron oxide (0,4 mol) and sulfuric acid 1 free acid (1,3 Several 47 mm diameter rings (as cathodes) are successively placed in a bath containing m/). The importance of pH has been recognized when plating commercially. pI (measured as 1.75) Ta. A shiny precipitate with a few matte spots was observed at 16OA/dm. and at a surface speed of 3 m/s. pH is approximately 1.8 (0.5 m As the free acid of l) increases, the precipitates on continuous carbon steel rings become almost It improved to a full shine and then began to take on a more matte texture.

Add sulfuric acid to bring the free acid to about 1.1 ml, and the adhesive bright plating is restored. It precipitated.

Tested the bright plating and found it to be extremely adhesive, 1o rating! ;u5850 0253(4) Corrosion resistant to nitric acid and resistant to high temperature oxidation I understand. The hardness is about 410 (Knoop) under a load of 1009, The base DPH was equal to 360 or Rockwell C-39.

Example 6 - Preferred alloy composition in chloride and sulfate baths A certain number of coatings were applied to 125 mm diameter steel rods, 25 mm long, with sulfuric acid having the following composition: Applications were made from solutions of salts and mixed acid salts/chlorides.

Chemicals Additives Concentration C9/l)) Chromium Chromium Chloride 394900 Chrome Value Chrome OO2639 Iron Ferrous acid 3 1 6.6 1 Nickel 45 11 11 5.6 Boric acid Boric acid 35 35 23 35 Ammonia Confucian Ammonium 14 14 8.5 13 Manganese manganese sulfate 0 0 2.2 3.3 type 04 stainless steel Alloy was used. The six parameters of the implementation are listed in Table 1. Ma in alloy sample The cancer content is less than 1% and therefore not reported.

1 203/4-13A0.45 160 62 2 1 53.7 1,6 44 ．． 7-14C1, 4310622226, 51,971, 6-19E1.8 1 60 62 2 3 21 2.2 57-18D1.5 160 62 2 3 4 41 55-18F1.65220 62 2 3 16 36 48 -19L1.8 160 65 2 3 8 48 44-20G1.8 16 0 50 2 4 31 7 62 The chromium content in alloy precipitates is Application conditions, e.g. current density, agitation, ratio of metal ions in pH 1 solution and metal It depends on the type of ion used to complex the ion. Sample 13A and sample When comparing 14G, pH is the main variable, and the chromium content is lower in pH It becomes high when (the acid content becomes high). This is for plating iron and nickel. It is known that the coulombic (cathode) efficiency of the membrane decreases at lower pH values. And it's reasonable.

Sample 18D and Sample 18F were plated under similar conditions except for current density. Conclusion The results show that the higher current density used for sample 18F results in higher chromatography. This resulted in a rum content.

Temperature also affects the percentage of chromium in the precipitate, Sample 19E and Sample 19L When comparing, increasing the temperature from 62C to 65C, and the chromium content in the precipitate decreased from 21% to 8%. Although temperature generally does not seem to be very important , higher temperatures are not favorable for chromium precipitation.

By varying some of the plating parameters, e.g. high pH, high chromium concentration, and both nickel and iron concentrations. By lowering the It is clear that it can be improved.

Generally, good bright and semi-gloss coatings are achieved at a pH of about 1.7 to 1.8. Obtained in clear precipitates - the actual ones have a matte texture and are thicker. Cracks occur in the thin coating.

Example 4 - Cr-Fe-Ni alloy in mixed chloride heptahydric acid bath Using a soluble filter type 04 stainless steel anode and a solution consisting of the following ingredients, Sample 202/98-14E was plated therein.

Chromium (chloride salt) 48.897e Iron (sulfate) 1.09/e Nickel (sulfate) 1129/e Houjo 35.097e I ammonium sulfate 5s, (Nl#13 The temperature was 62r and the pH was 14.

Using a cathode surface velocity of 2 m/s and a current density of 155 A/cm, 125 μm A coating was applied in 30 minutes. The relatively dense film had a matte texture on the surface. However, it generally does not contain any cracks and has a composition of 160r-21Ni-63Fe. It had

Example 5 - Fe-Cr alloy coating chromium (5651/e) and from chloride bath Iron (iron-chromium alloy coated at about 30C from a 529/6 chloride electrolyte solution) A film was deposited. Using the apparatus of Example 1 and removing the soluble 60/70 chromium-iron anode. The alloy coating shown in Table 2 was plated using (). Efficiency of cathode deposits chromium alloy It is conventionally defined as the percentage of applied current used to

Precipitation conditions Alloy composition current 97A 50.8 3. 0 2 9896G 22 0.6 40 2.4 6 9496B 36 0.6 80 2.4 8 9296D 40 0.7 160 2.4 18 82 These samples help us recognize the importance of pH. and within the broad scope of the invention, but outside the preferred pH range of the invention. be. However, the current density and efficiency of stirring and final alloy composition are The effect is 14 special table Showa 58500253 (5) It is clearly shown that the chromium content and efficiency of the deposit are proportional to the current density. Give an example. Low current density (and low agitation reduces efficiency and chromium percentage in the precipitate) By observing sample 97A where both are low, it is possible to use high current density and high agitation. Understand the importance of being present. Poor adhesion and thicker precipitates may cause cracking. Because of the shear, the precipitates are also restricted to very thin cross-sections. The coating is thin and contains chromium. Since the amount is low, corrosion resistance is poor.

Samples 96B, 96G, and 96D cracked at the periphery, but the rest were catalyzed chromium. The coating was suitable, similar to conventional hard chromium plating deposited in acid solution. analysis These cracks in the coating can be a negative influence when the main desired property of the coating is abrasion resistance. It will have no effect.

Example 6 - Fe-0r alloy precipitate filter 0/70 chromium-iron anode from sulfate bath and a sulfate solution to plate an alloy coating on the cathode of a copper-coated steel ring. Ta. The composition of the plating solution was as follows.

Iron metal ion 28 14 21 Chromium metal ion 26 39 47 The alloy coating was deposited at 5DC as shown in Table 6.

5 61F 1.5 160 2 1 20 8062P 2.0 160 2 1 ．． 26 7480D 1.9 230 3 2 24 7680E 1.9 3 10 3 2 48 5280F 1.8 390 3 2 42 5867C 1,7160326535 11B 1.8 160 3 3 29 7111A 161 160 3 3 26 7412A 1.745 160 3 3 32 68120 1.7 45 390 3 3 62 28 (some initial results (samples 61-80) , before confirming the importance of pH. Therefore, pH without extreme precision used a meter. Later, a more accurate instrument was used in place of this meter. Ta. Nevertheless, using divalent/diavalent chromium electrolytes, the preferred pH Outside the range, a thin matte coating was obtained. These coatings have a high chromium content, can be made by using high current density and high agitation.

As can be seen in Table 6, when using a less accurate pH meter, the results does not always match, but this allows you to measure the pH throughout the entire bath. This is attributed to the lack of sufficient precision in maintaining the pH. Accuracy is good This option is recommended when using a higher meter and when within the preferred pH range. It will be seen that superior control of the law can be achieved. For example, sample At 12A and 120, the pH is within the preferred range and the precipitate crystals are The ROM content thickens (increases) with increasing current density, for example, when the current density is 16O When increasing from A/dm2 to 39OA/dm2Vc, the chromium content increases from 62% It increased to 62% Or.

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Claims (1)

[Claims] 1. Plating consisting of iron ions, divalent chromium ions, and hexavalent chromium ions The aqueous solution is brought to a current density of at least about 75 A/dm and a pH of about 0.05 to 2.0. the cathode and the plating solution at a relative velocity of about 1 m/sec on the cathode surface. The chromium alloy film is deposited on the cathode at high speed by electrolysis while moving the How to electrodeposit. 2 Ions of additional alloying metals selected from nickel and/or cobalt The electrodeposition method according to claim 1, further comprising electrolyzing an aqueous plating solution containing . 6, about 209/(l or saturated divalent chromium ions and hexavalent chromium ions , from about 1 to 50971 iron ions and about 0 to 50'l/e nickel ions. 5 to 80% by weight of chromium, 20 to 9 Chromium alloy coating consisting essentially of 5% iron and 0-50% nickel by weight The electrodeposition method according to claim 2, characterized in that: 4. Complexes of mineral acids selected from sulfuric acid, sulfamino acid, hydrochloric acid, phosphoric acid and boric acid. Claim 1 comprising electrolyzing an aqueous plating solution further containing anion. Also, the electrodeposition method described in Po2. 5. The claim comprises maintaining the pH of the plating aqueous solution at about 1.7 to 1.8. Electrodeposition method according to box 1 or 2. 6. The anode is insoluble and inhibits the movement of oxidant to the cathode.8 This prevents the oxidation of divalent chromium and hexavalent chromium near the cathode. 6. The electrodeposition method according to claim 5, further comprising: Electrodeposition method as described in Box 1. 8, 20’! /e or saturated divalent chromium ion and trivalent chromium ion , consisting of 1 to 509/(l iron ions and 0 to 509/l nickel ions) , and the pH of the solution is within the range of 1.7 to 1°8, for chromium alloy electroplating. Aqueous solution. 9 Leadification of mineral acids selected from sulfuric acid, sulfamic acid, hydrochloric acid, phosphoric acid and boric acid The aqueous solution for chromium alloy electroplating according to claim 8, further comprising a negative ion. . 1