Stainless Steel Heat Exchangers is defined as a steel alloys with a minimum of 10.5%to 11% chromium content by mass. Stainless steel does not flake, rust or stain with water as regular steel does, but in spite of the name it is not fully stain-proof. Stainless steel is also called corrosion-resistant steel or CRES when the alloy type and not exhaustive, particularly in the aviation industry.