The anodic dissolution of iron—XI. A new method to discern between parallel and consecutive reactions

✍ Scribed by G. Bech-Nielsen

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 793 KB
• Volume: 27
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(82)80028-5

✦ Synopsis

It has been shown previously that in the steady state the behaviour of the iron electrode at low anodic potentials in perchlorate or sulphate electrolyte solutions may be characterized by two sets of parameters, depending upon the degree of deformation of the metal. Annealed iron will show a Tafel slope of CCI. 40 mV and a reaction order w.r.t. pH of 1 (Bockris-pattern), and strongly deformed iron will show a Tafel slope of ca. 30 mV and a reaction order w.r.t. pH of 2 (Heusler-pattern). Iron in an intermediate state will then show characteristics between the above extremes. The problem considered here is whether this behaviour is the result of a parallel combination of two independent reactions or of a shift in the rate determining step in one sequence of reactions (consecutive reactions).

A simple mathematical way of representing the two possibilities reveals a way of calculation eliminating the influence of pH on one of the associated terms. Thereby an earlier described method becomes available as a tool to obtain evidence of paraHel or consecutive reactions. The results are fully compatible with consecutive reactions taking place in solutions of perchlorate or sulphate.