Heat tint
Heat tint is the colored oxide layer that forms on a stainless steel weld from heat and air — from straw yellow through blue to gray. It shows how badly the weld is oxidized: any discoloration means chromium is used up and corrosion resistance is worse.
When you weld stainless steel, the weld gets glowing hot – and the hot surface immediately reacts with oxygen in the air to form a thin oxide layer. Depending on thickness, this layer shimmers in different colors: first straw yellow, then brown, blue, and finally gray. That's not just a cosmetic flaw, it's a warning sign. Because the oxide binds the very chromium that would otherwise form the protective . So every discoloration means: chromium is used up here, corrosion resistance is gone. Rule of thumb: The darker the heat tint, the worse the weld protects. That's why heat tints on stainless steel must be removed – mechanically or chemically – and the surface then .