Reinforcement corrosion leads into several damages which influence the structural load-bearing capacity, among which can be mentioned the cracking of concrete cover. This work study formulations to estimate the crack width of structural elements from the data of corrosion rate measured in two structural elements, made in 1990, with chlorides added in the concrete mix. These elements, one T beam and one column, were exposed at the atmosphere of Madrid, Spain. Two expressions have been fitted to the results: w = k Px / (c/f) and w = k Px / Ro, where w is a crack width in the time, k is a proportional factor, Px is the corrosion penetration in the time, c/f is the concrete cover/diameter relation and Ro is the original radius of the bar. The first expression has resulted the most adequate.