Stainless steel is one of the most resistant materials in chloride-containing environments and is an important material for water applications. The limiting conditions for pitting resistance of stainless steel depend on the alloying composition and the environmental condition. The pitting resistance increases with the increasing alloying level in terms of the Pitting Resistance Equivalent number (PREN). For the environmental condition, the chloride concentration, temperature, and the water system's oxidation potential also influence the risk of pitting corrosion which, if raised, would increase the risk of pit initiation and propagation.
This work aimed to develop a robust method for constructing pitting engineering diagrams and to understand the electrochemical techniques’ intercorrelation. Extensive electrochemical tests have been performed for a deeper understanding of the factors that affects the corrosion behaviour of stainless steel, which is correlated to the borderlines in the diagrams. The obtained result demonstrates that the electrochemical methods were sufficient to define pitting diagrams showing the boundaries between pitting and no pitting in terms of chloride concentration, temperature and the water system's oxidation potential. The laboratory long-term electrochemical test gives the best test method to simulate real applications and clearly shows the importance of an induction time for pit initiation.
Stainless steel is one of the most resistant materials to chloride environments and is an important material for water applications. Selecting a suitable stainless steel grade for water applications requires information about the performance of the candidate stainless steel grades. The limiting conditions for the pitting resistance of stainless steel depend mainly on the alloying composition of the steel and the surrounding environment. The pitting resistance normally increases with the increasing alloying level in terms of the Pitting Resistance Equivalent number (PREN). For the environmental condition, chloride level, temperature, and the water system's oxidation potential are factors that influence the risk of pitting corrosion which, if raised, would increase the risk of pit initiation [1-4]. Oxidizing species such as chlorine, typically used for water disinfection processes, are a significant factor leading to the ennoblement of the water system's redox potential. The redox potential increases with increasing chlorine levels and is typically in the range of 300-700 mV vs SCE for slightly chlorinated water systems [5]. This oxidizing effect of chlorine may have detrimental consequences, and stainless steel may suffer from localized corrosion if an inappropriate grade is used.
