ChemInform Abstract: The Effect of Phosphorus on the Mechanism of Intergranular Stress Corrosion Cracking of Mild Steels in Nitrate Solutions.

Abstract

ChemInform Abstract Upon corrosion of Fe-P alloys (0.003-2 wt.% P) in hot NH4NO3 solution, P impedes the formation of protective oxide layers on the surface. XPS results indicate that P in a negatively charged state (phosphide) is responsible for the reduced oxide growth. Constant strain rate tests on mild steels containing 0.003-0.05 wt.% P show a detrimental effect of phosphorus in nitrate solution in the potential range -300 mV to -100 mV vs. NHE. The effect is correlated to phosphorus segregated at the grain boundaries and can be predicted from the behavior of the Fe-P alloys. However, at potentials above -50 mV, the susceptibility of the steels to intergranular stress corrosion cracking is even higher and independent of the P content.