The initiation of localized corrosion with alloys exhibiting passive behavior has been studied extensively by the authors; first, with austenitic stainless steels1 and, more recently, with martensitic stainless steel2 and nickel.3 In all cases, it was observed that a go/no-go corrosion initiation threshold existed as a function of temperature, and a theoretical approach4 was developed to explain the stability boundary as the environment became more aggressive due to an increase in temperature or chloride concentration or a decrease in pH.
Because magnesium and magnesium alloys are expected to show passive behavior at high pH,5,6 it was decided to expand this approach to investigate the localized corrosion resistance of magnesium alloys. The ranking of alloys by this go/no-go methodology addresses only the resistance to the initiation of localized corrosion and not the subsequent kinetics of attack.
A series of preliminary experiments showed that the initiation of...
