Stainless Steel Surface Treatment

Commonly used stainless steel surface treatment techniques have the following treatment methods: ① surface natural whitening treatment; ② surface mirror bright treatment; ③ surface coloring treatment.

1.2.1 Whitening treatment of natural surface color: In the process of processing, stainless steel undergoes coiling, edge binding, welding or artificial surface fire-roasting and heating treatment to produce black oxide scale. This hard gray-black oxide scale is mainly composed of NiCr2O4 and NiF, two EO4 components. In the past, hydrofluoric acid and nitric acid were generally used for strong corrosion to remove. However, this method is costly, pollutes the environment, is harmful to the human body, and is highly corrosive, and is gradually eliminated. There are two main methods for the treatment of oxide scale:

⑴Sandblasting (pill) method: mainly adopts the method of spraying micro glass beads to remove the black oxide scale on the surface.

⑵Chemical method: use a non-polluting pickling passivation paste and a non-toxic cleaning solution with inorganic additives at room temperature for immersion. So as to achieve the purpose of whitening treatment of the natural color of stainless steel. After processing, it basically looks like a dull color. This method is more suitable for large and complex products.

1.2.2 Stainless steel surface mirror bright processing method: according to the complexity of stainless steel products and user requirements, mechanical polishing, chemical polishing, electrochemical polishing and other methods can be used to achieve mirror gloss. The advantages and disadvantages of these three methods are as follows:

1.2.3 Surface coloring treatment: stainless steel coloring not only imparts various colors to stainless steel products, increases the variety of products, but also improves the wear resistance and corrosion resistance of the products.

There are several coloring methods for stainless steel:

⑴Chemical oxidation coloring method;

⑵Electrochemical oxidation coloring method;

⑶Ion deposition oxide coloring method;

⑷High temperature oxidation coloring method;

⑸ Gas phase cracking coloring method.

A brief overview of the various methods is as follows:

⑴Chemical oxidation coloring method: It is the color of the film formed by chemical oxidation in a specific solution. There are dichromate method, mixed sodium salt method, vulcanization method, acid oxidation method and alkaline oxidation method. Generally "INCO" (INCO) is used more, but if you want to ensure the color of a batch of products are consistent, you must use a reference electrode to control.

⑵Electrochemical coloring method: It is the color of the film formed by electrochemical oxidation in a specific solution.

⑶Ion deposition oxide coloring chemical method: the stainless steel workpiece is placed in a vacuum coating machine for vacuum evaporation plating. For example: titanium-plated watch cases and watch bands are generally golden yellow. This method is suitable for mass product processing. Because of the large investment and high cost, small batch products are not economical.

⑷High temperature oxidation coloring method: It is to immerse the workpiece in a specific molten salt to maintain a certain process parameter, so that the workpiece forms a certain thickness of oxide film, and presents a variety of different colors.

⑸ Vapor-phase pyrolysis coloring method: more complicated, less application in industry.