Reliability of electrochemical methods applied to the study of Alumina coated stainless steel prosthesis

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Abstract
The corrosion resistance of alumina‐covered stainless steel prosthesis is discussed in this report. The test material was an AISI 316L steel with a plasma sprayed on alumina coating, applied directly or through an intermediate nickel base layer, whose mission is to guarantee a perfect adherence between the ceramic material and the steel. Use was made in the laboratory of Hank's solution as test medium since this solution is similar to organic fluids. In order to increase the reliability of the results the simultaneous use of various of the following electrochemical methods are recommended: Determination of corrosion potential with the time, polarization resistance method, coulostatic method and a.c. methods. The use of electrochemical methods to study ceramic‐covered stainless steel in the passive state poses some specific difficulties accruing from the disturbance of the working electrode by the applied electrical signals which limit the accuracy of the corrosion rate measurements. These difficulties do not appear in the case of a material having a intermediate layer which is more active.