Development of EPR technique for the control of cast alloys

The EPR DL (Electrochemical Potentiokinetic Reactivation Double Loop) techn ique enables the detection and quantification of de-chromed areas in stainl ess steel materials. This dechromisation results in a local destruction of the passive film around the chrome carbides or the intermetallic chrome-bas ed phases (phases sigma, chi ...) The conjunction of a corrosive mixture an d chrome-depleted areas gives rise to an intergranular corrosion phenomenon (IC). This work sums up the design of testing conditions for the EPR test with a view to controlling in situ the structure of cast materials. We searched fo r a sensitive enough electrolyte, as well as for operational conditions lea ding to an easy application on site. The study was carried out with two all oys: austenitic stainless steel CN-7M nickel based passivable alloy CW-12MW and was accompanied with the developm ent of a portable EPR cell for in-situ testing.