Corrosion of Carbon Steel and Cast Iron in a Gas Phase over Salt Melts Used in the Magnesium Industry

Resumo

Corrosion tests of SCh15 cast iron, St.3, and St.3 with an aluminized coating are performed in certain compositions of salt melts of 10% MgCl₂–KCl–NaCl and 10% MgCl₂–KCl–NaCl–CaCl₂ systems with concentrations of 10, 25, and 40% CaCl₂, as well as in the 10% MgCl₂–45% KCl–20% NaCl–25% NaBr melt and in a gas phase over these melts at 700°C. Corrosion rates of metallic samples are found by a gravimetric method. Concentrations of impurities of halogenides and hydrogen halogenides in air blown through a reactor with melts and samples are determined by the chemical analysis of absorption solutions. It is shown that the aluminizing of carbon steel can decrease the corrosion rate in a gas phase over a salt melt by a factor of 5–70. The mechanism of formation of gases aggressive with respect to carbon steel and cast iron in atmospheric air contacting with the salt chloride melt is considered. The acceleration of the formation of hydrogen chrloride and chlorine during the interaction of the salt melt with atmospheric air under the effect of corrosion products of iron is revealed.