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Why do stainless steel pipes get spots after cleaning?

May. 19, 2025

Stainless steel pipe fittings are a small part of the big family of pipe fittings. It is called stainless steel pipe fittings because it is made of stainless steel as raw material. There are many members in it, including common elbows, tees, crosses, stainless steel reducers, etc., all of which belong to stainless steel pipe fittings. According to the connection method, we can divide stainless steel pipe fittings into four categories: connecting stainless steel pipe fittings, threaded stainless steel pipe fittings, welded stainless steel pipe fittings and flanged stainless steel pipe fittings. The main stainless steel materials used to make stainless steel pipe fittings are 304, 304L, 316 and 316L.

So why do many gray-black spots appear on the surface of stainless steel pipe fittings when we use ultrasonic cleaning machines to clean them? In fact, this is an oxidation reaction. The chloride ions in the acid with strong oxidizing properties will pit the surface of stainless steel pipe fittings, forming gray-black spots that can be seen by the naked eye. However, it still depends on the specific situation. It depends on what state your stainless steel pipe fittings are in before cleaning, and finally determine what the reason is.

Cangzhou Aosendik Pipe Fittings Manufacturing Co., Ltd. is a large manufacturer specializing in the production of elbows, tees, reducers, elbows and caps. We can implement ASTM, ANSI, JIS, DIN, GB and other standards, basically covering all types of steel.

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