Corrosion of Stainless Steels...

Corrosion of Stainless Steels Stainless steels (SS) are alloys of iron (Fe) which containing a minimum of 10.5 % chromium (Cr). With increasing content of Cr and with the presence or absence of many of other elements, SS can provide an extraordinary range of corrosion resistance. Different grades of SS are being used since several years in atmospheres which are mild (open air, in architectural applications) as well as extremely severe (chemical-processing industries). Stainless steels are classified in five families as per the crystal structures and the strengthening precipitates. Each family of SS shows its own general features in terms of mechanical properties and corrosion resistance. Within each family, there is a range of specifications which varies in composition, corrosion resistance, and cost. Stainless steels are vulnerable to several types of localized corrosive attack. The avoidance of such localized corrosion is the focus of most of the efforts made in the selection of SS. Also, the corrosion performance of SS is strongly influenced by practices of design, fabrication, surface conditioning, and maintenance. The selection of a grade of SS for a specific application involves the consideration of several factors, but the main factor remains corrosion resistance. It is the first necessity to specify the likely service environment. Besides considering the design conditions, it is also necessary to consider the reasonably anticipated exposures or upsets in service conditions. The suitability of a specific specification can be assessed from laboratory tests or from the documented field experience in similar atmospheres. Once the specification with satisfactory corrosion resistance has been identified, it is then appropriate to consider other factors such as mechanical properties, ease of fabrication, the types and degree of risk present in the application, the availability of the necessary product forms, and cost. Families of...