Abstract
The location and frequency with which intergranular stress corrosion cracks initiate in sensitised stainless steels is, in general very difficult to predict. Many grain boundaries intersecting the free surface have the potential to initiate a crack but in most practical instances, significant cracks develop from a very small proportion of the available sites.
The ultimate objective of this work is to provide a quantitative, statistical description of the intergranular stress corrosion cracking of sensitised stainless steel, and to determine how these statistics vary systematically with externally controlled variables, such as the degree of sensitisation, the solution composition and hydrodynamics, and the electrochemical potential.
This paper describes the development of experimental techniques to detect electrochemical events - free corrosion potential fluctuations and current transients - which occurred on sensitised type 304 stainless steel during slow strain rate tests in very dilute, naturally aerated thiosulphate solutions, the events have been deduced to represent cracks which initiate, grow for a while and then repassivate. An estimate of the crack advance associated with a single event is given. Use of a digital tape recorder enabled current transients to be observed with high time resolution and their shape is commented upon.
