The main concern and consideration in civil engineering infrastructures are subjected to various climatic conditions environmental and atmospheric conditions, properties and behavior of metals and materials used in constructions. Studies on damage, deterioration and durability of components attract of civil engineers of today. Among the most pressing concerns for structural concrete durability is the corrosion of steel reinforcement. Concrete is a high alkalinity material. The pH of newly produced concrete is usually between 12 to13. In these range of alkalinity, embedded steel is protected from corrosion by a passivating film bonded to the reinforcing bar surface. However, when the passivating film is disrupted, corrosion may take place the damage caused by rebar corrosion in concrete structure has been considered as one of the major durability problem affecting the service life of concrete structures. Statics have indicated that cover 40% of failure of structure due to corrosion of reinforcement. Measurement of corrosion in concrete structures is a very important work for civil engineers. Half-cell is an instrument used to measure corrosion. It is a semi destructive testing instrument. This paper represent about the corrosion measurement in various Reinforced cement concrete elements. Using half-cell potential measurement and also explain how to measure the corrosion without breaking the concrete surface. That means how to convert the semi destructive testing instrument to non-destructive testing instrument.