Iron particles or other substances can become embedded in the stainless surface during fabrication or polishing operations. These particles must be removed or else they will cause discoloration, rusting, or even pitting. Oxidizing chemicals are used to form a passive layer along the surface of stainless steel to enhance resistance to corrosion. This process is the final preparation for stainless steel parts. It consists of immersing the parts in a nitric acid solution, rinsing with clear running water, and drying.