These visible colours, commonly referred to as heat tint, form during the welding process and are typically a result of oxidation at high temperatures. While they might look harmless or even decorative, the truth is they often point to reduced corrosion resistance and other. Each color provides insight into the temperature of the weld and reveals important information about the weld's structural integrity. As the metal is heated, it reacts with the atmosphere, so the molecular structure changes, creating a very thin oxidation layer. Each level of heat creates a different depth of oxidation that will reflect a specific wavelength. That is a good question, as many people have a misunderstanding of what the different colors in a stainless steel weld mean. Sometimes these hues are desirable and sometimes they are not. How they appear and why they matter depend on the process, material, industry and application.
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