Why do stainless steel precision castings rust?

Stainless steel precision castings are favored by consumers for their smooth appearance, corrosion resistance and precision forging. But in use, sometimes you will find yellow spots on the surface of stainless steel, just like rust, which does not make people wonder "Will stainless steel still rust?" Aiming at this problem, the editor will talk to you.

Professional stainless steel precision casting is resistant to atmospheric oxidation and corrosion. However, its corrosion resistance will change with the composition of the steel itself and the type of the surrounding medium. There is a very thin but thin and strong protective film (chromium-rich oxide film) on the surface of stainless steel precision castings, which can effectively prevent the infiltration of oxygen atoms and prevent the castings from continuing to oxidize. However, once this film is broken, the oxygen atoms in the molten metal in the gas will continue to infiltrate, or the iron atoms in the metal will separate to form a loose compound. In this case, the metal surface will rust, and the yellow casting will rust.

1. Environmental pollution

Polluted air contains a large amount of sulfate, carbon oxide, nitrogen oxide and other components. This substance will condense into water when it is cold, producing liquid spots such as hydrochloric acid, nitric acid, acetic acid, etc., which will cause chemical corrosion to castings.

2. Appearance of surface attachments

During the production process, acid, alkali, salt and other components may adhere to the surface of stainless steel precision casting parts, resulting in localized corrosion on the surface of stainless steel castings.

3. Electrochemical reaction

Attachments of dust or foreign metal particles containing other chemical elements pile up on the surface of stainless steel. In the humid air, the condensed water between the attachment and the stainless steel is connected to form a micro-battery, causing electrochemical corrosion, destroying the protective film, and causing the casting to "rust".

In order to ensure the luster of the metal surface, the rust of stainless steel castings is not impossible to remove. Stainless steel investment casting suppliers suggest that you can do this:

Frequently clean the surface of stainless steel castings, remove surface attachments, and eliminate hidden dangers that may cause corrosion of castings; for different regions, choose stainless steel of suitable materials. For example, 316 stainless steel must be used in beach areas, because 316 materials can resist seawater corrosion; when purchasing stainless steel castings, choose high-quality and reputable manufacturers to ensure that the quality of casting products meets industry standards.

Therefore, not any kind of stainless steel can resist corrosion and rust under any conditions. Stainless steel castings have exquisite craftsmanship and a wide range of applications. In order to manufacture high-quality stainless steel precision castings, pure stainless steel liquid must be used for casting in the production process.