Heat tints due to welding an their influence on the corrosion of high-alloy CrNi steels

High-alloy CrNi steels stand out for a high corrosion resistance due to a p rotective passive layer which forms with the content of chromium exceeding 13 %. When welding these steels, heat tints arise in the area of the welded joint which may range from faint yellow to intensive blue in the spectrum, depending on the applied welding process and the backing inert gas. Due to their structure, they partly drastically reduce the corrosion resistance o f CrNi steels so that they are a great problem in the technical application of welded components. In the following contribution the formation and stru cture of annealing colours is fundamentally described, particularly their i nfluence on the corrosion depending on the material and the welding technol ogy.