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​受付時間 9:00~18:00 
直通電話 090-6819-5609

mail:connection.fukui@gmail.com

亜鉛めっき(クロメート処理)

Details of galvanizing (chromate)

Galvanization (various chromate treatment)

Compliant with RoHS regulations (IEC62321 analysis results)

The reason why galvanization is excellent as a rust preventive film for iron and steel substrates is that zinc is electrochemically positive for the iron substrate, and the iron substrate is exposed due to film defects (scratches, cracks, pinholes, etc.). Even if it is, zinc itself has the property of sacrificing corrosion and preventing the formation of red rust on iron.

Galvanization has been a rapidly popular plating process since it was proven to be relatively inexpensive and the durability of zinc-plated and colored chromate-treated products applied to weapons during World War II in the 1940s.

Galvanized films are rarely used as they are plated, and are often used as finished products only after chromate treatment.

Therefore, the current situation is that the recognition as a post-treatment of chromate = zinc plating is low.

Zinc plating is a treatment that not only gives a beautiful appearance by chromate treatment, but also significantly improves color resistance.

There are colored chromate (chromate), glossy chromate (unichrome), black chromate, green chromate, etc. in the chromate film, and they are used properly for the purpose of corrosion resistance.

We can choose between hexavalent chromate and trivalent chromate.

Zinc plating-chromate treatment blog article

Post-processing is important as well as plating Blog articles

亜鉛めっきの防錆が優れている理由

鉄・鋼素地の防錆皮膜として亜鉛めっきが優れているのは、鉄素地に対して亜鉛は電気化学的に陽性となり、皮膜の欠陥(キズ、クラック、ピンホールなど)により鉄素地の露出している場合でも、亜鉛自身が犠牲的に腐食し鉄の赤サビ発生を防止する特性があります。この作用を犠牲防食と言います。

亜鉛めっきの後処理

亜鉛めっきは、亜鉛めっきのままので使用されることはほとんどなく、後処理(クロメート処理)を施してはじめて完成品として使用されます。

 

クロメート処理は美しい外観を得るだけではなく、耐食性を向上させる処理です。

クロメート皮膜には有色クロメート(クロメート)、光沢クロメート(ユニクロ)、黒色クロメート、緑色クロメートなどがあり、耐食性などの目的で使い分けます。

6価クロムのクロメート処理(RoHS非対応)、3価クロムのクロメート処理(RoHS対応)を選択頂くことが可能です。6価クロムのクロメート処理の方が3価クロムのクロメート処理に比べ耐食性に優れております。

Film characteristics

[Film hardness] Hv60-120

[Standard film thickness] 5 to 10 μm

Corrosion resistance evaluation

Salt spray test

Note: The values ​​in the table indicate the test time for white products before / and red rust after /. (Unit time)

Chromate treatment is applied to galvanization. Black chromate is K, green chromate is G, glossy chromate is B,

Colored chromate is represented by adding C to the end of the plating symbol.

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  090-6819-5690

 

​受付時間 9:00〜18:00

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ご質問回答
 01 

Q. There are some galvanized (black chromate) products with tight tolerances (φ14 + 0.018 / 0).

Is it possible to control the film thickness? (Example: 10 ± 1 μm?)

A. Although it is necessary to perform actual processing and confirm by actual dimensional measurement, it is possible to keep it within the tolerance range.

Regarding the film thickness, it can be handled with a film thickness of about 8 ± 2 μm.

 02 

Q. Is it possible to use electroless nickel plating of 3 μm or more on the inner surface of the STKM pipe and zinc nickel plating of 5 μm or more on the outer circumference (Ni elution rate 15 ± 3%)?

A. We have considered the treatment method.

From the conclusion, it is possible to respond to inquiries with electroless nickel on the inner surface of the pipe and zinc nickel plating on the outer circumference of 5 μm or more (Ni elution rate 15 ± 3%).

 03 

Q. Is it possible to consistently handle S10 material products from MFZnNi-C (zinc-nickel alloy plating) 5 to 10 μm → trivalent unichrome → chromate and then acrylic silicon coating?

A. We have confirmed the content of your inquiry.

It will be handled by barrel plating, but it is possible to handle it according to the processing content that you have consulted.

 04 

Q. Is it possible to use zinc-plated (Ep-Al / Zn2 trivalent black chromate) trivalent black chromate on aluminum A2017 products?

A. It is a zinc-plated black chromate on aluminum, but it cannot be processed directly, but it can be handled by forming a base with a different metal.

 

 05 

Q. I would like to apply zinc plating to the zinc die-cast (zinc die-cast: ZnDC) material. Is this possible?

A. Zinc plating is available for zinc die-cast materials. Please tell us about the specified film thickness and chromate treatment.

 06 

Q. I am considering galvanizing electrical components, but I am concerned about conductivity.

The material is an iron-based material, but what is the conductivity when comparing the material as it is and galvanized?

A. When comparing the conductivity of galvanized and iron-based materials, there is almost no difference, so there is no decrease in conductivity.

Since iron materials are prone to rust, the electrical resistance of the surface increases when rust occurs, but by applying zinc plating (chromate treatment),

Since it is less likely to corrode, it is possible to maintain conductivity.

 07 

Q. When I used a galvanized spring washer, it cracked when tightened.

We are considering baking as a countermeasure, but it has been a long time since the plating process, but is it effective?

A. It is probable that the material that has been hardened by quenching absorbs hydrogen during the pickling and plating processes and becomes brittle, causing cracks during tightening. Since the occluded hydrogen can be removed by heat treatment (baking), it is necessary to perform heat treatment to remove hydrogen as soon as possible after plating for materials with Rockwell 40 or higher.

If time has passed after plating, the brittleness will not disappear even if heat treatment is performed.

In such a case, the brittleness may be alleviated by peeling off the plating, tempering to the extent that it does not deviate from the lower limit of the specified hardness, applying zinc plating again, and immediately performing heat treatment.

 08 

Q. I am considering soldering to a galvanized (colored chromate) product, and I tried soldering, but the solder bounces and I cannot join. Is it possible to do soldering?

A. It is difficult to solder joint if chromate treatment is applied.

Hexavalent chromium present in the chromate film forms an oxide film, which improves corrosion resistance, but is thought to reduce solder bondability.

If solder bonding is required, solder bonding is performed in a zinc-plated state without chromate treatment.

It is possible to solve the problem by applying zinc plating (chromate treatment) to the entire surface with the solder joint applied first.

 09 

Q. Is there an easy way to distinguish between galvanizing and cadmium plating?

A. If you have a fluorescent X-ray measuring device, you can measure metal components with fluorescent X-rays.

If you don't have a fluorescent X-ray measuring device, you can dissolve the film, but you can check it by immersing it in hydrochloric acid.

With zinc plating, it reacts immediately after immersion and hydrogen gas is generated violently.

In the case of cadmium plating, it gradually dissolves.

 10  

Q. I would like to apply paint to a product that has been treated with colored chromate, but the adhesion between the paint and the colored chromate is poor. Is there any way?

A. When painting a colored chromate-treated product, I think that adhesion can be ensured by applying a base treatment such as an etching primer before painting.

If it is difficult, it is possible to apply the paint directly by removing the colored chromate (including zinc plating).

Since it is necessary to use strong acid to remove colored chromate, we can only peel it off if you ask us.

 11 

Q. I have galvanized products with many blind holes, but after drying, the holes are rusted.

Is there any way to improve it?

A. The cause of rust inside the hole after drying is thought to be that there is little or no plating deposit inside the hole.

As an improvement method, it can be improved by increasing the precipitation of plating inside the hole, but in the case of a blind hole, the amount of plating liquid coming in and out is small.

Since the distance from the electrode is long, it is difficult to improve by the usual method, but it is thought that by increasing the total film thickness, the precipitation inside the hole will be improved from the current one.

 12  

Q. We are considering galvanizing cast iron, but when other companies have previously applied zinc plating to cast iron, we have experienced stains and unprecipitation due to aging. Is there any such problem? ??

A. There are two types of zinc plating, alkaline and acidic, and alkaline has characteristics such as excellent uniformity and excellent appearance.

The acidic type has characteristics such as hydrogen brittleness is unlikely to occur, and it is possible to apply good plating to cast iron materials.

Since you are requesting zinc plating on cast iron this time, we will support it with acidic type zinc plating, so we think that it is possible to suppress the stains and unprecipitation that occurred before.

 13  

Q. It seems that there are too many copper ions in the galvanized bath, and black discoloration occurs on the plated surface.

Is there a way to get rid of this copper ion?

A. It means that the galvanized surface turns black, so it is possible that copper ions will increase as you say.

As a method of removing copper ions, it can be removed by dry electrolysis at a low current density.

 14  

Q. With zinc plating (cyan bath), the low voltage part turns black during chromate.

Could you please tell me the cause and countermeasures?

A. It is said that the low-voltage part becomes black due to the zinc plating of the cyanide bath, so it is necessary to confirm by analysis, but it is thought that the cause is that the copper ions in the plating solution are increasing.

Copper ions can be removed by dry electrolysis with weak electrolysis or by adding zinc powder and filtering.

 15  

Q. When evaluating hexavalent colored chromate and black chromate in the salt spray corrosion resistance test, which one is inferior in corrosion resistance?

A. Colored chromate has better corrosion resistance.

Since black chromate contains heavy metals such as silver, its corrosion resistance is slightly inferior to that of colored chromate.

 16 

Q. The product before galvanization was exposed to chromate treatment liquid (hexavalent), and the product was thoroughly washed and galvanized.

Adhesion is poor and swelling occurs. Is there a way to prevent swelling?

A. It is said that the hexavalent chromate solution has been applied to the product before galvanization, so the applied part is in a state of chromate treatment. Therefore, by pickling the material with hydrochloric acid, the chromium ions on the surface can be removed and the poor adhesion is improved.

If you peel off the currently treated zinc plating with hydrochloric acid, you can just wash it with water and apply zinc plating to finish it without any problem.

 17 

Q. The galvanized product was not handled properly and was scratched, exposing some of the material.

Is it possible to partially repair it?

A. If only the chromate treatment is scraped (zinc plating remains on the base), there is a method to correct only the chromate.

Since it is a complicated process such as immersing the product in a strong alkaline solution, it is better to peel off everything including zinc plating once and then re-plat it from the viewpoint of appearance and corrosion resistance. ..

​ 18 

 

Q. I have galvanized iron bolts with barrel plating, but the nuts do not pass after plating, and even if the plating is peeled off, the nuts do not pass.

Did the bolt expand during galvanization?

A. Since the processing temperature of zinc plating is as low as about 20 ° C, it is unlikely that the bolt will expand due to zinc plating.

Due to the treatment with barrel plating, collisions when products are taken in and out, collisions between products during barrel plating, and collisions during drying if a centrifugal dehydration dryer is used for drying, etc. It is thought that the cause is deformation due to impact.

This is especially noticeable for products with large bolt sizes, so it is necessary to consider the treatment method.

 19 

 

Q. I am treating high carbon steel with a zinc-plated cyanide bath), but I cannot partially treat it.

Why is it only partially plated?

A. As the carbon content increases, more hydrogen precipitates than metal precipitates from the cyanide bath, resulting in partial plating.

 20  

 

Q. I am considering galvanizing (black) SUS304. Is it possible to process it?

A. Some processing manufacturers refuse, but we can handle it.

 21

 

Q. Is it possible to galvanize the aluminum material (A5052)?

A. It is not possible to directly galvanize the aluminum material, but it is possible to process it by applying nickel plating to the base.

As a caveat, nickel plating is applied to the base, so the film thickness of the base becomes thicker.

 22

 

Q. Is it possible to support MFZnII-C?

A. MFZnⅡ-C is available.

For chromate treatment, you can select the hexavalent chromium type that conflicts with RoHS and the trivalent chromium type that does not conflict with RoHS.

Please tell us which one you prefer.

 23

Q. We are considering zinc-nickel alloy plating for STKM pipes.

Is it possible to respond? Also, is it possible to handle zinc-nickel alloys with a Ni eutectoid rate of 15 ± 3%?

A. It is possible to plate STKM material with zinc-nickel alloy with a Ni eutectoid rate of 15 ± 3%.

We would appreciate it if you could tell us about the film thickness and quantity.

 24

Q. Is it possible to support MFZnII-C (trivalent chromate) for SUP (spring steel)?

A. Supports MFZnII-C (trivalent chromate) for SUP (spring steel).

 25

Q. I would like to apply zinc-nickel alloy plating to zinc die-cast (ZnDC). Is this possible?

A. Zinc-nickel alloy plating is available directly for zinc die casting.

We would appreciate it if you could tell us about the specified film thickness and the specified chromate treatment after plating with zinc-nickel alloy.

 26  

Q. I would like to express a color such as fluorescent color on the S45C. Is there any good processing?

A. It is possible to express a glossy color with colored zinc plating.

Expressions such as red, pink, blue, and green are possible.

 27  

Q. Is it possible to support shot blast + MFZn2-G (Black) processing for SPCC-SD of about 970mm?

A. Shot blast + MFZn2-G (Black) processing is available for long products.

 28 

​​

Q. I would like to apply zinc plating (unichrome treatment) to zinc die-cast (ZnDC). Is this possible?

A. We have a track record of zinc plating (unichrome treatment) on zinc die casting in the past.

It can be processed without any problem.

We would appreciate it if you could send us materials that show the shape of the product.

 29   

​​

Q. Is it possible to apply color treatment to the S45C cap bolt?

A. Colored zinc plating is available for color treatment of cap bolts.

The colors can be red, pink, and green.

 30  

Q. Is it possible to apply matte galvanized stainless steel (SUS304)?

A. Matte galvanized stainless steel is available.

The matting method is matting with shot blast.

 31  

Q. It is a product made of iron material shaped like a small button, but there are many and there are no holes for hanging, but zinc plating is

Is it possible?

A. Since it is a small button shape, it can be handled by barrel plating (plating in a special container).

Since barrel plating can process a large number of products at once, it has the advantage of being cheaper than rack processing (holding and processing each product one by one).

There is.

The disadvantage is that the products collide with each other in the container, resulting in scratches and dents.

 32  

Q. Is electrozinc plating Ep-Fe / Zn 5 / CM2 (trivalent) available for chrome molybdenum steel (SAE4130)?

A. Electrozinc plating on chrome molybdenum steel Ep-Fe / Zn 5 / CM2 (trivalent) is available.

 33 

Q. Is it possible to peel off the zinc from a galvanized steel sheet with dimensions of 1800 x 1000 t0.4 mm?

A. Zinc peeling can be applied to galvanized steel sheets.

Rust will occur as soon as the zinc on the galvanized steel sheet is peeled off, so please let us know what to do with the post-treatment.

 34  

Q. What kind of processing is MFZn2-G?

A. It is electro-zinc plating on iron material (minimum film thickness 5 μm) + green chromate treatment.

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Connection Co., Ltd.

Please feel free to contact us for plating, coating, polishing, heat treatment, etc.

Consultations and quotations are free.

​4-202-5 Shizugaoka, Fukui City, Fukui Prefecture 910-3635 (Japan)

​Reception hours 9: 00-18: 00 

Direct phone 090-6819-5609

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