Effect of four coating structures on corrosion kinetic of galvanized reinforcement in concrete

Abstract

In the present work is described the effect of the characteristics of the galvanized coating on corrosion rate of reinforcing bars embedded in a concrete without additives and in another with $2\%~~CaCl_{2}$ in terms of cement weight. To this end, the following materials were subjected to the action of a moisture saturated atmosphere for a period of $400$ days: an annealed-galvanized coating; another one obtained by dipping in a molten Zn bath with $0.025\%$ Al and some others produced at $450$ and $430^{o}C$ in an ordinary bath.

The attack evolution vs time was controlled by measuring the polarization resistance. The electrochemical determinations were gravimetrically verified and supplemented by a metallographic examination of tests coatings.

In the absence of chlorides, the attack is fully tolerated. Chlorides radically change the corrosion behaviour of galvanized steel and increase the attack by a factor of $2.8$ in the most favourable case, but in these conditions, coatings with thick, homogeneous $\eta$ layer outperform the usual ones, and specially the annealed ones.