Cyclic polarization applied to industrial corrosion inhibitors in order to measure their localized corrosion inhibition ca pability.

摘要

It is well known that the most damaging form of localized corrosion in recirculating cooling systems is pitting corrosion. Corrosion rates inside pits can reach up to 100 times those of general corrosion. If localized corrosion occurs on the heat exchanger plate of a cooling system, it is very likely that in the absence of proper treatment, pits will extend right through the plates leading to a general failure of the cooling system. The consequent costs and demand for non-renewable resources associated with premature asset replacement can be very significant. Traditional strategies used to control general corrosion are well known and very effective. However, chemical technologies aimed at protecting mild steel surfaces against pitting corrosion in aqueous environments and that exhibit an undeniable effectiveness, have yet to be discovered. This paper outlines a new methodology to evaluate the performance of various compounds in terms of localized corrosion inhibition. The electrochemical technique used is cyclic polarization applied to a 3-electrode cell. It is complemented by an observational protocol that allows a degree of statistical analysis to be carried out on the pits formed during the anodic polarization (maximum pit depth and pit depths' distribution). After the review of some experimental considerations, the cyclic polarization technique is discussed in order to justify the proper choice of electrochemical parameters. The indicators of the intensity and of the industrial criticality of localized corrosion that can be extracted from the data are also discussed. Furthermore, some reflection on how these indicators can be used to evaluate the effectiveness of a compound at inhibiting localized corrosion is presented. Finally, data gathered from the analysis of a series of pre-selected inhibitor compounds are presented, analyzed, and discussed.