POTENTIAL DECAY BEHAVIOR OF IRON IN DILUTE NITRIC-ACID

Potential-time decay curves were used to investigate the passivation o f iron in dilute nitric acid solutions of different concentrations. Th e effect of sulfate ions on the decay curves was also examined. It was observed that the decay curves formed an almost flat potential segmen t ending after reaching the Flade potential (the potential at the end of the plateau). The duration of the plat eau was a function of both t he initial holding potential and the acid concentration. The addition of sulfate ions affected the decay duration without interfering with t he Flade potential. This is worth noting in view of the well-known dep endence of the open-circuit potential decay on both pH and on the cons tituents of the solution.