Published: Jan 1991
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The corrosion behavior of low carbon steel in wet residential building thermal insulation and filtered insulation leachates were investigated with variable access of air to the corroding interface. Aqueous environments were characterized in terms of solubility of leachable species, pH and specific resistivity. Several electrochemical methods were used to evaluate the general corrosion behavior and to estimate the corrosion rate. Direct corrosion rates were determined by weight-loss and comparisons made to rates in wet cotton using distilled water. Although the pH of the environments varied from 4 to 9.5, a major variable is access of oxygen to the metal interface. This was confirmed by studying the effect of depth of embedding and by partial embedding of steel specimens in wet insulation. Limiting oxygen concentrations in leachates were established by air and nitrogen sparging which changed the corrosion rate by factors greater than ten. An additional variable is the effect of composition of the leachate on the adherence and porosity of the corrosion product deposit. Electrochemical polarization measurements provided information on the corrosion mechanisms.
wet insulation, steel corrosion, aeration, deaeration, corrosion mechanism
Professor Emeritus, University of Tennessee, Knoxville, TN