INVESTIGATION INTO THE ACTIVE PASSIVE TRANSITION OF 304 STAINLESS-STEEL IN ORGANIC MEDIA CONTAINING WATER PART 2. INFLUENCE OF WATER ON THE ACTIVE DISSOLUTION AND PASSIVATION

The influence of water on the corrosion and passivation of type 304 stainless steel has been studied in deaerated ethanolic solutions containing hydrogen chloride. The potentiostatic polarisation curves show that both, critical current density for passivation and passivation potential, strongly depend on the water content of the solution. A passivation model based on the assumption of a reversible primary passivation potential explains this influence of water and allows the determination of other kinetic parameters. The propounded passivation model also explains the result that the part of “passivated” surface at the maximum current density is the same for all water contents examined. The dominating influence of the water content is shown more clearly when measurements from methanolic and propanolic solutions are concerned. The passivation potential only depends on the water content and not on the type of alcohol.