Why It May Be Necessary to Remove Heat Tint from Stainless Steel
Heat tint refers to the change in the surface colour of stainless steel due to the thickening of the chromium oxide layer on the surface of the heat-affected zone. DIY fabricators may not be sure whether they should remove the heat tint after they have completed welding a stainless-steel product that they have been fabricating. This article discusses two circumstances that may make it necessary to remove the heat tint from the surface of stainless-steel products.
Stainless steel may reflect certain colours, such as pale yellow, depending on how thick the oxide layer on its surface is. It is also possible for stainless steel surfaces to reflect light so that a viewer sees the different colours of the rainbow on that material. Heat tint can interfere with the uniformity of the colours reflected by the stainless steel product. This is because the thicker oxide layer in the weld zone will have a different colour from the rest of the material.
That colour variation should therefore be removed in order to regain uniformity in the appearance of the stainless steel product. Heat-tint removal is particularly important if a clear sputter coat is going to be applied on the stainless steel. That clear coat will reveal the underlying appearance of the stainless steel. This makes it necessary to ensure the product has a uniform surface appearance.
Corrosion Resistance Restoration
Fabrication enthusiasts should also consider removing the heat tint if they are going to use the product in an environment where corrosion is a major threat, such as during the transportation of fluids. The heat tint is formed when chromium is drawn from beneath the surface of the stainless steel. Consequently, the metal just underneath the surface of the stainless steel will have a reduced ability to resist corrosion due to the depletion of chromium from that sub-surface area. Removing the heat tint helps to restore a balance in the distribution of chromium within the metal because chromium will "creep" from other parts of the metal so that the entire product has uniform protection from corrosion.
Heat tint can be removed from the heat-affected zone of stainless steel products in several ways, such as immersing the product in a nitric acid solution. However, those tint removal processes may be too complex for a hobbyist because incorrect application can cause the surface of the product to pit. It is therefore advisable for you to ask custom stainless steel fabrication experts for help so that you don't ruin the products that you have just fabricated.