Electrochemical behaviour of a type 302 stainless steel in a stress field

The 302 stainless steel type samples, were subjected to a U-bend test and the electrochemical behaviour of both the compressive and tensile strained surfaces of the samples were studied in a normal sulphuric acid bath. For this, the polarization curves I = f(E), and current-time curves I = f(t), were plotted separately for the concave and convex sides of each specimen. It was found that, the critical current density Ice, and passive current density Ip, are slightly less for the sides under compression than for the sides under tensile stress. Afterwards, some samples were subjected to a buckling test and the variation of electrode potential of each one of both sides of the samples stressed by buckling was studied separately. The obtained results show that the application of a tensile stress always leads to a decreasing potential of the convex side of samples; whereas a compression stress leads the potential of concave sides to more noble values. Therefore, it was shown that an assembly of two identical electrodes, electrically isolated, bent and immersed in the solution forms a differential stress cell with an electromotive force about thirty mV in equilibrium. (C) 2000 Kluwer Academic Publishers.