Comment on “EIS and XPS study of surface modification of 316 LVM stainless steel after passivation” by D. Wallinder, J. Pan, C. Leygraf and A. Delblanc-Bauer

摘要

If the factual results presented in this paper arc not questionable and may interest specialists of passive layers, the general conclusions which are drawn from these results are misleading. In addition. the legend of Fig. 3 is incomplete (2 definitions for 4 curves) and this does not facilitate comprehension of the paper. From our past experience [1]. the “a” and “b” in this Fig. 3 probably refer to the grit finish in Table 2, and the high and low open circuit potentials (OCP) should respectively correspond to specimens with and without further treatment in HNO_3. However, such an ennoblement does not necessarily represent an improvement of the corrosion resistance. In fact, this kind of “overpassivation” is well known in the industry. In particular, it is also found in neutral chloride- bearing media. where it proves to he highly detrimental [1]. On the other hand. the quantities in Figs. 4, 5, 6, 9 and 11 are expressed in electric units. μA/cm~2 and kΩ-cm~2, supposedly more “scientific”. but without any reference to the practical significance of their magnitude. This is a very common criticism made to microbiologists studying microbial corrosion [2]. Unfortunately, the trap also applies to corrosion scientists overly confined in a laboratory, so that it has been felt necessary to emphasise it explicitly in corrosion teaching [3].