Tribocorrosion d’un acier inoxydable en milieu marin artificiel

Corrosion wear of stainless steel inartificial sea environment

¹ DGA/DCE/Centre technique d’Arcueil
² Laboratoire de Mécanique des Solides, CNRS UMR 7649, École Polytechnique, Palaiseau
³ Travail effectué à DGA/DCE/Centre technique d’Arcueil, actuellement : PSA/Direction des moyens techniques, La Garenne Colombes

Abstract

The friction and wear of stainless steels in sea-water environment is of prime interest for naval applications. The behaviour of the tribosystem alumina pin / 316L stainless steel disc in a 30g/l NaCl solution buffered at pH 8 exhibited the coupling between mechanical and electrochemical parameters. One objective of this study is to determine methods for the comprehension and interpretation of tribocorrosion tests.

The friction coefficient is quite sensitive to the applied potential and it is particularly true around the free potential under friction. In our experimental conditions, sliding friction shifts the value of the free potential towards more cathodic value. This behaviour shows the sensibility of potential to frictional perturbation of the surface. In passive domain of materials, an increase of intensity is observed under friction. This evolution is due to depassivation / repassivation phenomena. The overall wear volume shows a dependence to the applied normal load and to the imposed electrochemical potential. Except for the beginning of the test, the evolution of wear is linear in time during a 5 hours test.

The total wear, addition of mechanical and electrochemical wear, is investigated and an explanation of its global behaviour is proposed on the basis of an electrochemical and mechanical framework. This eroded volume can be principally attributed to corrosive mechanisms. A mechanical modelling related to evaluation of elasto-plastic pressure distribution is proposed and gives the stabilised wear regime. The experimental wear regime is in agreement with this model.

The simplicity of this tribocorrosion system allows an automatic analysis and interpretation of tests results. Interactions between electrochemical and mechanical behaviour are studied. We can explain the mechanical wear by study of contact problem and electrochemical wear by analysis with Faraday law. Despite the great complexity of industrial problems (wear and corrosion of two antagonists,...), this method could be adapted to interpret various tribotest systems.