Inhibition of localized corrosion in chromium containing stainless alloys

The application of stainless steels and chromium containing nickel-based alloys is limited by their susceptibility to localized corrosion in the forms of pitting and crevice corrosion or environmentally assisted cracking. Inhibitors may be normally found in service environments or added on purpose to mitigate or avoid the effects of aggressive agents such as chloride ions. The present study critically reviews the present knowledge on inhibition of chloride-induced pitting and crevice corrosion. Pioneering studies and recent findings are analyzed in light of the present theories for describing the localized corrosion processes. This review particularly focuses on the inhibition of crevice corrosion of alloy 22, which has been thoroughly studied in the past decade.Fil: Rodríguez, Martín Alejandro. Universidad Nacional de San Martín; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentin

Factors influencing corrosion of metal pipes in soils

Deterioration of buried metal pipes due to corrosive soil environment is a major issue worlwide. Although failures of buried pipe due to corrosive soil is an old problem, yet such failures are still uncontrollable even with the application of advanced corrosion protection technologies. Therefore, understanding factors causing corrosion of buried pipes is necessary. This article reviews factors causing corrosion of buried pipes in soils. Factors include moisture content, soil resistivity, pH, dissolved oxygen, temperature and microbial activity. Moreover, we discuss the influence of manufacturing method and the comparison of corrosion behaviour of cast iron, ductile and mild steel pipes. We found that corrosion rate of pipes increases with moisture contents up to the critical moisture value. Although pH affects corrosion, there is no relationship between corrosion and pH and the corrosion rates of buried pipes are inversely proportional to soil resistivity. Soils containing more organic matter show high resistivity. Dissolved oxygen in soil develops differential cell which accelerates corrosion of metallic pipe. Different types of bacteria present in soil develop biofilms on metallic pipes, which deteriorates pipes with time