Although the steel rebar's natural tendency is to undergo corrosion, the alkaline environment of concrete (pH of 12 to 13) provides steel with corrosion protection. At this high pH, a thin oxide layer forms on the steel and prevents metal atoms from dissolving. This passive film does not actually stop corrosion; but it reduces the corrosion rate to an insignificant level. Because of concrete's inherent protection, reinforcing steel does not corrode in the majority of concrete elements and structures. Corrosion can occur only after the passivating layer is destroyed. Now if the concrete layer around the rebar is thin and wears quickly, then salt can get to the rebar and begin to corrode.