EFFECT OF ADDITION OF CHROMIUM AND MOLYBDENUM ON THE CORROSION BEHAVIOR OF AMORPHOUS FE-20B, CO-20B AND NI-20B ALLOYS

A comparison of the corrosion behavior of three series of amorphous boron-bearing alloys in 1 N HCl has been performed as a function of the content of chromium and molybdenum. The addition of up to 20 at.% of chromium to the alloys does not effectively increase the corrosion resistance. Within this range of chromium content, the corrosion resistance is mainly determined by the anodic stability of the alloy: the more noble the alloy, the lower the corrosion rate. The addition of 30 at.% or more chromium and the combined addition of chromium and a small amount of molybdenum to iron- and cobalt-base alloys leads to a sharp decrease in the corrosion rate, while the addition of large amounts of chromium and molybdenum is necesary to increase the corrosion resistance of nickel-base alloys. Because the beneficial effects of chromium and molybdenum appear after they react with the environment, the more active the alloy, the more effective the addition of these elements. © 1979.