Application of the electrochemical microcapillary technique to study intergranular stress corrosion cracking of austenitic stainless steel on the micrometre scale

The electrochemical microcapillary technique was applied for the first time to study the electrochemical dissolution signals from single growing cracks due to stress corrosion cracking of thermally sensitised AISI 304 stainless steel in potassium tetrathionate solution. Potentiostatic current measurements on initiating cracks along grain boundaries were performed. Typical current signals of potentiostatic and potentiodynamic measurements consisted of a series of current peaks showing fast rise and exponential decay, sometimes interrupted by passive phases. The results indicate that stress corrosion crack growth is a discontinuous process of passive and active phases, which might be explained by the film rupture model.

► SCC of AISI 304 stainless steel was studied with electrochemical microcapillaries.
► Current signals of single growing stress corrosion cracks were tracked.
► Single cracks grow stepwise and show passive phases between active dissolution.
► From current signals and crack lengths a dissolution front of 80 nm is calculated.
► The results are in accordance with the film rupture model for IG SCC.