Explanation

alloy materials that exhibits excellent resistance in various corrosion environments or under the action of corrosion and mechanical stress factors at the same time. Various metals show different corrosion resistance behaviors in different environments. These behaviors are affected by several key factors, including the thermodynamics stability of the metal itself (usually divided into four categories according to the standard potential), the transformation from activation or conditioning to passivation of the metal, the protective performance of the corrosion product film generated on the metal surface, and the impurities or second equivalent factors that can form an effective cathode in the metal. Therefore, the principles for developing corrosion resistant alloy include the following: improving the thermodynamics stability of metals or alloy. The cathode activity and anode activity in alloy are reduced. The dense corrosion product protective film is formed on the surface of alloy. These goals can be achieved by alloy, heat treatment and other methods. Taking iron base alloy as an example, the addition of Cr, Ni, Mo, Cu, Si and other elements can not only improve the corrosion potential of alloy, but also promote the passivation of alloy and form a good protective film. There are many kinds of corrosion resistant alloy, which can be divided into iron based alloy, nickel based alloy, copper based alloy, aluminum based alloy, magnesium based alloy, other non-ferrous metals and their alloy, rare metals (such as W, Mo, Ta, Nb, Ti, Zr, etc.) and their alloy, as well as precious metals and their alloy according to their compositions. According to the structure of corrosion resistant alloy, it can be divided into homogeneous alloy, binary alloy with anode base (such as Mg Al alloy), binary alloy with cathode base (such as Cu Zn alloy) and complex multiphase alloy.

Classification