Chemical surface treatment of Japanese steel drums

[Japan] Suzuki Yuki

As a representative of the Technical Committee of the Japan Steel Barrel Association, I hope to discuss it with you on the topic of "chemical surface treatment of steel drums".

1. Production process and chemical conversion treatment of barrels

First, I will give a general introduction to the production process of steel drums. The production of the barrel includes shearing steel plates, which are cut and rolled from the coiled steel sheets according to a fixed length, and then welded by electric resistance welding, followed by stamping.

In addition, the top of the bucket and the bottom of the bucket are stamped into a top cover and a bottom cover by a coiled steel plate, and the top end is punched into two standard flange holes of a standard size. Then, the top and bottom of the barrel are transferred to a surface chemical treatment process, which is the focus of this article.

Finally, the barrel and the bottom and top of the barrel are assembled and sealed. The production of the front section of the steel drum is completed.

Second, the current status of Japanese barrel chemical treatment

1. In Japan, most steel drum surfaces are chemically treated.

2, the following is the type of chemical treatment

(1) Most methods using zinc phosphating

(2) There are also a few methods of using iron phosphating

3. Chemical treatment is also used by most steel drums as pretreatments for the inner coating.

Now, my focus is on "chemical treatment issues." In Japan, most steel drum manufacturers are chemically treated on their steel drums, usually using both zinc phosphating and iron phosphating, the former being more common than the latter.

Chemical surface treatment is also a method used by international steel drum manufacturers for surface coating of steel drums.

Third, the purpose of the chemical treatment method

1. Japanese steel drum buyers are required to have no grease or dust in the steel drum provided by the steel drum manufacturer.

2. Therefore, the steel drum must be degreased, degreased and cleaned, otherwise the steel drum will easily rust.

3. Chemical surface treatment is to prevent rust after degreasing and cleaning the surface of the steel drum.

Next, I will explain this link in detail.

In Japan, steel drum buyers usually provide manufacturers with strict steel drum standards. These require that the barrel be cleaned, but the dust and grease present in any country's raw materials are inevitable. Therefore, the steel drum must be strictly degreased and cleaned, and the surface of the steel sheet is also prone to rust before forming. Therefore, chemical treatment is an important method to protect steel drums from rust.

Fourth, the effect of chemical surface treatment

1. Anti-rust in the degreasing treatment and steel drum filling stage

2. Continuous cleaning of steel drums (oil and cleaning effects)

3, the durability of the film

4, keep the steel barrel excellent appearance

The chemical treatment of the surface of the steel drum can reduce the rust in the production and use of the steel drum (when the manufacturer and the purchaser fill the steel drum) the inside of the steel drum is clean, because before the chemical surface treatment, these steel drums are Degreasing and cleaning. The coating on the inner and outer surfaces of the steel drum has a good durability, especially the strength and adhesion of the coating, because they have been coated with a chemical surface, so they have a beautiful appearance, even if they are not painted. The inner surface of the barrel is also covered by a chemically treated rustproof film.

5. Chemical surface treatment process

Now, I will explain the chemical surface treatment process.

The chemical surface treatment process is applied to three aspects, namely the barrel body, the top and the bottom, and the most significant effect is embodied in the barrel.

Six, chemical processing equipment

This picture shows the process from the inside out. The processing equipment consists of a tunnel in which the treatment fluid flows from top to bottom and from left to right.

This picture shows the appearance of the processing equipment, which can be chemically surface treated by the appearance, barrel, top and bottom.

7. Zinc phosphating and iron phosphating process

1. Zinc and iron phosphating processes

This figure shows the process of zinc phosphating and iron phosphating, respectively.

Bright gray is zinc phosphating, and blue-violet is iron phosphating.

2, features

The table above illustrates the galvanized and iron-coated process and their respective characteristics.

This zinc and iron film is formed by crystallizing zinc or iron ions.

3, the film picture of the scanning microscope

Zinc phosphating treatment

These images were obtained using a scanning microscope, indicating that the surface of the steel drum was treated separately by zinc phosphating and iron phosphating.

This picture of zinc phosphating shows crystals like white needles. Therefore, the zinc-based phosphating film is formed by zinc crystallization.

On the other hand, the picture of the iron-based phosphating film treatment only shows the surface of the steel sheet, not all of which is formed by the treatment of the iron-based film.

4. Crystal structure of zinc-based film

These characteristics indicate the crystal structure of the zinc-based phosphating film. The zinc-based phosphating film contains zinc phosphate and zinc iron phosphate in a ratio of about 7:3.

Eight, improve the corrosion resistance of phosphating film

1. Rusting through condensation in steel drums

If the temperature of the air rises, when the steel drum has been produced at high temperature and high humidity, condensation is formed on the inner surface to cause rust. Next, an example will be given to improve the corrosion resistance treatment of the zinc-based phosphating film.

If the temperature in the air is reduced after the steel drum is at a high temperature and high humidity, the water droplets may form rust spots on the inner surface of the steel drum. Use this example to show that rust spots are formed by condensation.

2, through the condensation of rusty factors

We have considered the factory to pass the condensation rust factor.

In this respect, the abscissa indicates that the concentrations of chloride and sulfate ions are replaced by zinc ions during the final cleaning process, and the ordinate indicates the process by which the circulating dry and wet air is exposed to produce rust. The abscissa indicates the treatment of the barrel which has been washed with a high concentration of chloride ions and sulfate ions during the zinc phosphating process.

3, deionization effect

At the A plant, the concentrations of chloride and sulfate ions in the final wash water were 18 ppm and 24 ppm, respectively. Therefore, there are few harmful ions in the discharged wastewater of the factory, and the corrosion resistance of the film on the surface of the steel drum has been greatly improved.

Parts of the steel drum

Therefore, we treat harmful ions in the plant and consider several different methods to remove chloride and sulfate ions in the final wash.

This feature indicates that the deionization effect has been applied to the production of rust prevention. In the A plant, industrial water is often used in the final cleaning of chloride and sulfate ions. As a result, the process of rust has been greatly reduced and the effect is clearly demonstrated.

Nine, conclusion

1. Most steel drums in Japan are chemically surface treated.

2, chemical surface treatment can play a temporary role in rust prevention, cleaning inside the barrel and filling the barrel with goods.

3. Anti-rust is continuously improved by phosphating solution in the process of chemical surface treatment.

Now, let me sum up this theme. Most steel drum production in Japan has to undergo chemical surface treatment to clean the inside of the steel drum, and the effect of temporary rust prevention is in the internal steel drum cleaning and user filling time. Deionized water is used in the final water rinse chemical surface treatment process, so the rust prevention of the steel drum can be greatly improved.

The film provided by treatment with zinc phosphate is formed from zinc phosphate crystals to a thickness of about 0.6 microns. It temporarily protects the steel drum that has not been filled with any filler and improves the durability of the coating film. Steel drums covered with zinc phosphate membranes are mainly used for containers of general chemicals and resinous liquids.

On the other hand, the iron-based phosphating film is not crystalline, and its thickness is only about 0.06 μm. Its thickness is one tenth of the thickness of the zinc-based phosphating film. Although it does not have an important influence on the formation of the primer film, it has only one rust-proof effect. The steel drum is mainly used for packaging such as lubricating oil and zinc-free solution after phosphating.

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