How to deal with the surface damage of large stainless steel flange?
Flange de-rusting method: immerse the flange in hydrochloric acid, the principle is to reduce the rust to iron, but there are dangers in this method. Hydrochloric acid is a corrosive substance, which is harmful to human body. During operation, pay attention not to touch the human body, and neutralize the finished flange with alkali, not directly.
Ordering requirements and inspection after fabrication can prevent and find the existence of free iron. ASTM standard A380  specifies the rust test method for inspecting iron or steel particles on stainless steel surface. This test method should be used when there is no iron. If the results are satisfactory, wash the surface with clean, pure water or nitric acid until the dark blue disappears completely. As pointed out in standard A380 , if the rust test solution cannot be completely removed, it is not recommended to use this test method on the process surface of the equipment, that is, the direct contact surface used to produce human consumer goods. The simple test method is to expose in water for 12-24 hours to check whether there is rust. The experiment is not sensitive and time-consuming. These are inspection tests, not cleaning methods. If iron is found, it must be cleaned by the chemical and electrochemical methods described later.
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