The effect of fluoride on corrosion of reinforcing steel in alkaline solutions

The influence of fluoride content of alkaline solutions on the corrosion of reinforcements has been studied, by means of electrochemical techniques, in saturated solutions of Ca(OH)2 and same pH NaOH solutions with additions of NaF, thus simulating the liquid phase of concrete. Fluoride can be present as a minor component in low-energy cements. The joint presence of chlorides and fluorides in the corrosion process of steel has also been analysed. It has been established that fluoride anions are able to produce pitting of reinforced steel in alkaline media of high pH. In Ca(OH)2 saturated solution, the precipitation of CaF2 lowers F- concentration below the minimum that promotes a pitting corrosion process; if there is not enough Ca(OH)2 to precipitate all F- ions, the presence of fluoride in these media causes an increase in passive film dissolution and corrosion rates. © 1994.Peer Reviewe