New test Methods for promoting sustainable Corrosion Resistant Alloys in harsh industrial environments

Purpose and goal

The aim was to develop test methods for evaluating the corrosion resistance and possible ranking of highly alloyed stainless steels and nickel based alloys. The project managed to define methods which enable for the industrial partners to perform ranking tests for these highly corrosion resistant materials. Development of a stricter test protocol and the application of the test methods to a larger set of materials is required for full implementation.

Expected results and effects

Methods for testing and ranking of stainless steels and nickel based alloys for corrosion resistance were successfully used in the project. In concentrated CaCl2 solutions, pitting corrosion was obtained for all materials. The Critical Pitting Temperature were found to depend on the potential applied while the Critical Pitting Potential depended on the test temperature. Concentrated MgCl2 was tested but was not aggressive enough with tested parameters. The outcome of the pre study can be used by the project members as a tool for ranking of more corrosion resistant materials.

Planned approach and implementation

Three different highly alloyed stainless steels and one nickel based alloy were tested in concentrated CaCl2 and MgCl2 solutions. Electrochemical methods were used; polarisation at fixed potential with increasing temperature (Critical Pitting Temperatures, CPT), polarisation at fixed temperature with increasing potential (Critical Pitting Potentials, CPP) and current monitoring at fixed temperature and potential. All the experiments were performed in an Avesta cell and the corrosion was assessed optically.