Surface Oxidation Tint
Surface discoloration due to heat is a discoloration of the weld surface and heat-affected zone caused by insufficient trailing shielding gas. It indicates corrosion susceptibility in high-alloy materials.
Physicochemical mechanism of action
Surface heat tint occurs when the weld surface and the heat-affected zone are not sufficiently shielded by shielding gas after welding. This leads to rapid oxidation of the metal surface, resulting in a blue or gray discoloration.
Metallurgical relevance & risks in welding
Surface heat tint can increase the corrosion susceptibility of the weld, especially in high-alloy materials such as steel or nickel alloys. This can lead to long-term degradation and cracking, which impairs the service life of the component.
Workshop practice & instructions
To avoid surface heat tint, it is important to ensure a sufficient shielding gas post-flow of at least 10 seconds. This can be checked using a shielding gas flow meter. For high-alloy materials, the post-flow should be even longer to create a complete oxidation protection layer.