Microelectrochemical corrosion study of super martensitic welds in chloride-containing media

Pitting corrosion was studied in welded joints of supermartensitic stainless steels. The electrochemical behavior of three different weldment zones (weld metal (WM), parent metal (PM) and heat affected zone (HAZ)) was characterized independently using an electrochemical minicell through potentiodynamic and potentiostatic techniques. The minicell design selected for this work has the additional advantage of showing promise for service application. Macro-electrochemical characterization was also used to provide a basis for comparison and check the effectiveness of minicell techniques in characterizing the corrosion resistance of welded super martensitic stainless steels. Minicell experiments exhibit a great capacity to discriminate between the different welding zones. The electrochemical response can be correlated with the microstructure of the different zones. Thermal cycles resulting from the welding procedure do not have an important effect on the amount of retained austenite or on the values of the pitting potential EP in the HAZ.

► Minicell system is capable of discriminating between the different welding zones.
► Welding thermal cycles do not affect significantly pitting potentials in the HAZ.
► Pitting susceptibility is comparable in the HAZ and the PM.
► WM metal exhibits enhanced pitting resistance due to higher Mo content.