New Inhibitors for Crack Arrestment in Corrosion Fatigue of High Strength Steels^* Available to Purchase

It has been shown that the fatigue life of a high strength Type 4340 steel exposed to high humidity is reduced by an order of magnitude when compared to dry ambient air. This has been directly attributed to the effects of corrosion and hydrogen embrittlement. In the present work, the principles of process control, which affect the electrochemical reactions occurring at the tip of the advancing crack, are integrated with the metallurgical concepts of the stress cracking phenomena to develop new crack arrestment compounds. The concept of phase transfer catalysis has been used to solubilize inorganic inhibitors into an organic phase. This enabled the inhibitor ions to remain free of hydration shells and become more effective inhibitors. It has been demonstrated that a number of combinations of compounds such as those containing dichromate, borate, and nitrite, or nitrite, borate, and cerate have been very successful in retarding the fatigue crack growth rate of Type 4340 steel exposed to 90% relative humidity.