Question

Can one get the repassivation potential of a stainless steel in a saline solution using the linear polarisation method (LPR)?

Explain your answer in 1-2 sentences.

Answer 1

The resistance of austenitic stainless steel type 304 to pitting corrosion was studied in solutions of sulphuric acid (2M and 5 M) with and without sodium chloride addition by linear polarization technique by R.T. Loto (J. Mater. Environ. Sci. 4 (4) (2013)448-459 ISSN: 2028-2508 CODEN: JMESCN.)

The pitting and passivation potentials, corrosion rate and current density were analyzed with respect to the chloride ion concentration. Under anodic polarization the stainless steels in sulphuric acid solution acquired a passive state, with breakdown at the transpassive region (pitting potential), however this was greatly reduced with the addition of sodium chloride which led to a sharp increase in current at potentials significantly lower than the value that necessitates pitting in the acid media due to rapid breakdown of the passive film and development of local pits. Results obtained establish the dynamic relationship and interaction between the sulphate/chloride ion concentration and electrochemical potentials in the corrosion behavior of the ferrous alloy at ambient temperature.