The anodic index is a measure of the corrosion resistance of stainless steel. It is determined by measuring the potential difference between the stainless steel and a reference electrode in a solution of sulfuric acid and hydrochloric acid. The higher the anodic index, the more corrosion-resistant the stainless steel.

The anodic index is a useful tool for selecting stainless steels for applications where corrosion resistance is important. For example, stainless steels with a high anodic index are often used in the food, beverage, and pharmaceutical industries, where corrosion resistance is essential to prevent contamination of products.

The anodic index of stainless steel can be affected by a number of factors, including the alloy composition, the heat treatment, and the surface finish. By carefully controlling these factors, it is possible to produce stainless steels with a high anodic index and excellent corrosion resistance.