Corrosion of Alloy Steels...

Corrosion of Alloy Steels Alloy steels consists of a group of steels which shows mechanical properties superior to those of ordinary carbon (C) steels as the result of additions of certain alloying elements such as chromium (Cr), nickel (Ni), and molybdenum (Mo) etc. Total content of the alloying elements can range from 0.5 % to 1 % and up to levels just below that of stainless steels. For many alloy steels, the primary function of the alloying elements is to increase the hardenability in order to optimize mechanical properties and toughness after heat treatment. However, in some cases the addition of the alloying elements is used to reduce atmospheric degradation of the steel under certain specified service conditions. Alloy steels are used in a broad range of applications. In some cases, corrosion resistance is a major factor in the selection of alloy steels, while in other applications; it is only a minor consideration. The information available on the corrosion resistance of alloy steels is end use oriented and often addresses rather specialized types of corrosion. Many applications use steels with a rather low content of the alloying elements, high strength low alloy (HSLA) steels, and structural alloy steels. Small additions of some alloying elements usually enhance corrosion resistance in moderately corrosive environments. However in severe environments, the corrosion resistance of this group of steels is often no better than that of C steels. Certain applications need more highly alloyed steels which, in addition to achieving the required mechanical properties, provide increased resistance to specific types of corrosion in certain environments. In this group of steels, corrosion resistance is also an important factor in alloy design. Corrosive environments and the use of the alloy steels Atmospheric corrosion is a factor in nearly all applications of...