A Study of Acid and Base on Corrosion of Steel Embedded in Concrete

Corrosion can be defined as “The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of material and its properties”. In concrete, corrosion is an electrochemical reaction driven by the difference in electrical potential between metal and concrete surface. It has been well known that steel embedded in concrete is in the passive state, due to the high basicity of sodium hydroxide medium. Thus, the steel is not subject to corrosion and possesses almost unlimited durability. Since steel in concrete structures are in passive conditions, steels are protected by a self-renewable thin oxide layer promoted by the concrete alkalinity. Corrosion can initiate only when passivity is destroyed. There are two main causes of reinforcement corrosion both of which involves the passivating layer of the iron oxide around the reinforcement. The first is carbonation of concrete (i.e. the reaction of atmospheric CO2 with cement paste, which lowers pH value of medium and causes general corrosion to produce a mild acid called carbonic acid).This book is an attempt to provide the knowledge of measurement of corrosion.