JPS63230885A - Surface treatment of metal - Google Patents

Abstract

PURPOSE:To considerably improve the corrosion resistance of various metallic materials by forming an iron-zinc alloy film on the surface of each of the materials by mechanical plating, chromating the film and coating the resulting composite film with a resin film forming agent. CONSTITUTION:A blasting material obtd. by coating iron cores with zinc is projected on the surface of a metallic material to form a porous iron-zinc alloy film. This alloy film is chromated to form a chromate film not only on the surface of the alloy film but also in the micropores in the porous film. Thus, a composite film consisting of zinc and a chromium compd. is formed on the surface of the metallic material. The composite film can provided corrosion resistance. In order to obtain satisfactory corrosion resistance in severe environment, the composite film is further coated with an org. or inorg. resin film forming agent consisting of a methyl ethyl ketone-based solvent and epoxy resin, silicone resin or the like.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a metal surface treatment method that is commonly used for various metal materials and has excellent corrosion resistance, chemical resistance, oil resistance, weather resistance, etc. It is something.

(b) Conventional technology and its problems When using iron-based metal materials, rust prevention must be taken into account. Therefore, the surface is treated with anti-rust oil, painting, phosphate coating, etc. In addition to this, the anti-corrosion coating method is also used, but this method has the problem of hydrogen embrittlement associated with the plating process. To compensate for this, baking treatments and the like are used, but it is not perfect, and plating may not be possible depending on the material.

For this reason, stainless steel is used in some parts to improve its corrosion resistance, but its corrosion resistance is not always satisfactory. In other words, improving workability may deteriorate corrosion resistance, or In some cases, electrolytic corrosion may accelerate the corrosion rate of the mating material. Furthermore, the material costs are high, which limits the cost, so in reality, it is not widely used.

(c) Means for solving the problems This invention was made to solve the above-mentioned drawbacks, and it goes without saying that the corrosion resistance is improved.

It satisfies all conditions such as chemical resistance, oil resistance, weather resistance, and heat resistance.

That is, a plastic material having an iron core and a zinc coating is applied onto a metal material, and a chromium compound is formed on the surface of the metal material by forming a composite pattern made of zinc and chromium compounds. Alternatively, the present invention provides a total bending surface treatment method in which a film is formed by applying an inorganic resin film forming agent.

The present invention will be described in more detail below. When a ferrous metal material is used in a corrosive environment, if corrosion occurs on the surface, the strength will deteriorate or break due to the corrosion fatigue phenomenon. For this reason, various methods of rust prevention have been studied2, such as applying rust preventive oil, painting, or using a phosphate coating, but all of these methods cause tension, compression, friction, etc. due to external forces. In some cases, the coating peels off, etc., and the rust prevention is not satisfactory. In addition, some materials have improved corrosion resistance by plating, but the process inevitably causes deterioration of the material due to hydrogen embrittlement due to hydrogen infiltration. In addition, there are methods such as bluing by heat treatment and resin coating, but these also have unsatisfactory corrosion resistance due to peeling of the coating due to tension, compression, and friction.

Recently, a series of innovative plating methods that broke the conventional wisdom regarding plating technology have been developed and are being put into practice (Special Publications No. 59-9).
No. 312), the method uses iron or an iron alloy as a core, and uses an iron-zinc alloy layer around the core to coat zinc or a zinc alloy, thereby producing a plastic material consisting of an aggregate of independent particles (No. 312). A method (hereinafter referred to as Mechanical P f
(abbreviated as MP method) and has many absolute advantages such as low installation cost, low energy consumption, and few environmental pollution factors.

The coating formed by this MP method, that is, the iron-zinc alloy coating (hereinafter referred to as MP coating), has a structure in which minute pieces of iron-zinc alloy are layered on the metal surface, and is porous as a whole. form).

This treatment method provides the above-mentioned porous iron-zinc alloy coating on the metal surface, and this coating essentially refers to an MP coating.

By the way, in general, a zinc-based plating film alone is unlikely to rust at a relatively early stage, and this also applies to the MP film formed by the above-mentioned MP method. In order to prevent the occurrence of rust, it is desirable to combine some sort of post-treatment with a thin film treatment.

Therefore, as a result of various investigations and studies in order to find a thin film treatment that achieves especially excellent corrosion resistance in combination with the above-mentioned MP coating, the inventors decided to apply chromate treatment to the MP coating using an aqueous or non-aqueous treatment liquid. It has been discovered that by doing so, it is possible to ensure extremely good corrosion resistance.

Chromate treatment coatings have traditionally been applied to galvanized coatings (molten galvanization, electrogalvanization), but the corrosion resistance improvement effect of MP coatings is different from that of the above-mentioned normal galvanized coatings. It belongs to
exceeds common sense predictions. This is due to the characteristics of the MP coating itself; in other words, the coating is porous, unlike general plating coatings, and when aqueous or non-aqueous chromate treatment is applied to it, it can cause damage not only to the surface of the coating but also to the surface of the coating.

It is thought that the chromate film penetrates into the microscopic voids inside the porous structure and forms a chromate film, which exerts a barrier effect and improves the anticorrosion effect.

The reason for this can be considered as follows.

Since a normal film obtained by electroplating is dense, when it is subjected to chromate treatment, both the lower plated film and the upper chromate film have a thin plate shape. In such a coating structure, if a flaw occurs that reaches the plating base, the chromate coating will not function effectively and will not be repaired sufficiently, which will cause deterioration of corrosion resistance.

On the other hand, if a chromate film is formed based on the above-mentioned porous film and penetrates into the micropores inside the film, for example, even if a large flaw that reaches the base material occurs,
It is considered that the chromate coating inside the porous body functions effectively without being significantly destroyed, and the bottom is repaired in a sufficient manner, thereby maintaining good corrosion resistance.

Also, for metal materials, static loads and impact loads.

In the case of a film with a structure based on a porous film impregnated with a chromate film, which is subjected to stress such as repeated loads, it must be able to withstand stress, such as elastic deformation such as tension and compression. MP Coating - Chromate coating has a durable coating that will not crack or peel.

As mentioned above, this is based on a porous MP coating made of plastic that has excellent adhesion to the base material, and on top of this, a chromate coating is applied not only to the surface of the porous coating but also to the microscopic voids inside. Due to the penetrating shape, the so-called vertical network structure is strengthened and exhibits excellent non-peelability. Therefore, it has the effect of withstanding the elastic deformation of tension and compression required of fully bendable materials.

By the way, the size of each individual particle of the iron-zinc plastic material varies depending on the properties of the projected surface, etc.
Approximately 16 meshes (1μφ) or less are appropriate, and the material of the plastic material should be 50 to 70 wt% iron and 30 wt% zinc, depending on the performance of the formed film and the blast processing conditions.
-" Approximately 50 wt% is appropriate. Furthermore, the amount of adhesion of this MP coating is 3 g/rd or more, preferably 6 to 3 g/rd.
It is preferable to set it to about 0g/+d.

That is, if it is less than 3 g/rrr, no substantial effect on corrosion resistance can be obtained, and the effect of the combination with the chromate treatment film is small.

A chromate treatment film is attached to the porous MP film formed as described above, but this chromate treatment is generally
It is classified into three types: seizure type, ■strong reaction type, and ■weak reaction type. A brief explanation of each is as follows.

(2) The baking-type chromate treatment liquid is a mixture of a water-soluble chromic acid compound, a reducing agent, and water, which is applied to the surface of the object to be treated (using a roll coater, dipping, etc.), and then baked and heated. By heating,
The water-soluble chromic acid compound is reduced to form a chromate film.

■Strongly reactive chromate A treatment solution consisting of a mixture of a water-soluble chromic acid compound, strong acid, and water is used, and this is applied to the surface to be treated (dipping, spraying, etc.) to dissolve the zinc on the surface and reduce chromium. A reaction occurs to form a chromate film.

■Weakly reactive chromate treatment solution is a mixture of a water-soluble chromic acid compound, a weak acid such as an organic acid, and water. After applying this to the surface to be treated, water is dried and evaporated to form a chromate film.

Basically, any water-based chromate treatment can be used as mentioned above, but these three types have some drawbacks in terms of equipment, economy, corrosion resistance, stability of chromate film formation, etc. be. Taking these points into consideration, it is most preferable to employ processing based on the conditions shown below.

That is, chromic acid compound 0.1-50g/1. Sulfuric acid 0
．． A water mixture containing 01 to 5 g/l is used as the treatment liquid.

This is a method of contacting for 0.5 to 8 seconds. this is,
Especially considering the compatibility with porous MP coating.

These conditions were discovered by the inventors through experiments. As for the type of treatment liquid, it basically succumbs to the strong reaction type, but the amount of strong acid is much smaller than that of general ones, and the contact time is also extremely short. However, it is distinctive. If this method is adopted, no baking treatment is required, which eliminates the need for equipment and energy, and compared to the general strong acid type, elution of the MP coating during the treatment process is suppressed and the formation of the chromate coating is stable. However, because the reaction product is reduced by the short treatment time, subsequent washing with water can be omitted, and what is particularly noteworthy is that in combination with a porous MP coating, extremely excellent corrosion resistance is achieved.

Here, as the processing conditions for this special reaction type, the amount of chromic acid compound is 0.1 to 50 g/j! , sulfuric acid 0101
The reason why a water compound containing ~5 g/It was used as the treatment liquid and the contact time was set to 0.5 to 8 seconds is as follows.

In other words, if the amount of chromic acid compound is less than 0.1 g/1, the amount of chromium deposited will be small and the corrosion resistance will be low.
When the amount exceeds 1, the chromate reaction is promoted and the MP odor is dissolved. Therefore, the amount of chromic acid compounds is
0.1 g/l, preferably 1.0-10 g/l.

In addition, the amount of sulfuric acid was set to 0.01 to 5 g/β.
．． If it is less than 01, the chromate treatment becomes easy to elute.

On the other hand, when it exceeds 5 g/It, the chromate reaction is promoted,
This is because the MP film melts. In addition.

Preferably it is 0.1-1 g/l.

In addition, the reason why the contact time was set to 0.5 to 8 seconds is that if the contact time is less than 0.5 seconds, the chromate solution will not penetrate sufficiently into the MP coating layer, whereas if it exceeds 8 seconds, the MP coating will This is because the reaction and dissolution progresses, resulting in significant deterioration of the treatment solution.

The amount of the aqueous chromate treatment film is not particularly limited, but in practice it is suitably 305 g/rrr or more, preferably 60 to 300 tsg/rd.

In other words, if it is less than +30+wg/rr1, the contribution to corrosion resistance is low, and if it is less than +605g/rd, sufficient effects cannot be obtained.On the other hand, if it exceeds 300mg/rd, the elution rate of chromium increases, which is particularly disadvantageous in terms of pollution. becomes.

In addition, there are also non-aqueous chromate treatments that use halogenated solvents such as trichlorfluoroethane and alcohols, which are almost the same as aqueous chromate treatments in terms of corrosion resistance. Depending on the properties, aqueous and non-aqueous systems are selected as appropriate.

By applying the above MP coating treatment and 12. chromate treatment, it was possible to form a composite coating consisting of zinc and chromium compounds on the surface of the metal material and impart corrosion resistance, but these treatments cannot be performed under even harsher environments. However, it is not always sufficient to do so alone, so it is possible to form a film by applying an organic or inorganic resin such as a silicone resin or an epoxy resin to a solvent mainly composed of methyl ethyl ketone.

It has been found that chemical resistance, oil resistance, and weather resistance are improved.

Furthermore, the characteristic feature is that when this film-forming treatment is applied, it is heat resistant, and 1* treated materials, such as paint,
It has excellent adhesion to the resin coat.

(d) As the example test piece, a cold rolled steel plate of 75 x 150 x 20 was used, and it was subjected to MP treatment and chromate treatment under the conditions shown in Tables 1 and 2 to obtain a total coating weight of 100a+g/
The film formation amount is about drrf, and this is used as MP-1, M
It was named P-2.

Table 1 (MP treatment) In addition to this, 103 (product name of Toagosei Kagaku Kogyo Co., Ltd.), which mainly consists of silicone, which is commercially available as an organic and inorganic resin film forming agent, and AM3 (product name of Toagosei Chemical Co., Ltd.) which mainly consists of fluororesin (Nippon Acheson) (product name) was applied under the conditions shown in Tables 3 and 4, respectively, to obtain Ni Coat and F Coat. Table 5 shows the results of SST and CCT tests performed on each of these test pieces.

Table 3 (K Coat) Table 4 (F Coat) Table 5 (E) Effects of the Invention From the above, MP treatment and chromate treatment are performed to form a composite film consisting of zinc and chromium compounds on the surface of metal materials.9 Next, by applying an organic or inorganic resin film forming agent to form the film, it has better corrosion resistance (S
ST test) was significantly improved. Furthermore, it is also found that it has excellent weather resistance (OCT test).

Furthermore, if two types of organic or inorganic resin film forming agents are applied in combination, the effect will be even more pronounced.

Claims (1)

[Claims] A plastic material containing iron as a core and zinc coating is applied to the metal material, and a chromate treatment is performed to form a composite film of zinc and chromium compounds on the surface of the metal material, followed by formation of an organic or inorganic resin film. A metal surface treatment method in which a coating is formed by applying an agent.