Inhibitoren der Korrosion 17(1) Die Bedeutung des „Hart-Weich-Konzepts”︁ von Pearson für die Erkennung von Struktur-Wirkungsbeziehungen von Inhibitoren bei der Korrosion des Eisens in NaCl-Lösungen bei Gegenwart von Sauerstoff

Corrosion inhibitors 17 The importance of pearson's “hard-soft-concept” with respect to the recongnition of relationship between structure and activity of inhibitors of the corrosion of iron in sodium chloride solutions in the presence of oxygen On the base of a previously published postulate according to which Pearson's hard-soft-concept may form the base for finding inhibitors for specific applications it is shown with the aid of model inhibitors with “hard” functional groups that it is indeed feasible to derive defined relations between the structure and the activity of inhibitors. The hard groups used were the phosphoryl ?P(O)O and the carbonyl ?C?O groups. It has been shown that such compounds are able to form very stable and protective surface layers on iron and that the efficiency of the inhibitors clearly increases with increasing length of the aliphatic chain. As has been shown by eletrochemical measurements these acids have a bearing on the rest potential as well as on the current-potential behaviour; this fact points to rather variable compositions of the surface layer. In the case of polyfunctional acids sterical factors may have a bearing on inhibitor efficiency, too.