Atmospheric corrosion of zinc Part 2: Marine atmospheres

Abstract

This paper summarises the results obtained in the MICAT (Mapa Ibero-Americano de Corrosão Atmosférica (Latin American Map of Atmospheric Corrosion)) atmospheric corrosion project (an Iberoamerican project on atmospheric corrosion, involving 14 countries and 75 atmospheric test sites) for zinc specimens exposed in the Latin American region for 1–4 years at 23 pure marine and 19 mixed marine (i.e. SO₂ polluted) sites. The atmospheres at these sites were characterised climatologically and in terms of their pollution levels so that their corrosivity could be expressed in accordance with ISO standards. Morphological and chemical characterisation of the zinc corrosion product layers (ZCPLs) was performed using scanning electron microscopy coupled with energy dispersive spectrometry (SEM–EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and soluble salt evaluation techniques. The results obtained show that the corrosion rate of zinc is a function of both the chloride pollution level and the time of wetness. Some synergetic effects of Cl^- and SO₂ were demonstrated, although some special types of behaviour were also observed.

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