Changes in corrosion rates in atmospheres with changing corrosivity

Abstract

This paper presents a study on the atmospheric corrosion of carbon steels, zinc, copper and aluminium in the industrial atmosphere. Trends representative for Central Europe are evaluated on the results for the Czech test site Kopisty. The climatic data and levels of pollutants, namely SO₂, have been measured, collected and analysed over 25 years. The corrosion rate of structural metals is significantly affected by SO₂ and the metals quickly react to the decrease of SO₂. The corrosion of both newly exposed metals and surfaces formerly exposed to polluted environments slowed when SO₂ pollution in the atmosphere was reduced. The study does not reflect the effects in atmospheric corrosion systems with dominating chloride influences (marine and marine–industrial atmospheres). The chemical composition and morphology of the corrosion product layers of zinc, copper and aluminium are presented and compared. The comparison of the corrosion rates and corrosion product compositions of zinc after 1, 20 and 100 years of exposure is presented.