Intercalation in zinc-layered hydroxide : Zinc hydroxyheptanoate used as protective material on zinc

During transport or the storage, galvanized steel products undergo wet storage stain phenomenon, leading to the formation of an extensive white rust of zinc. The corrosion products are mainly zinc layered hydroxides salts of which allow several intercalation or coprecipitation reactions allowing the easy absorption of corrosive anions on the surface and then the corrosion of zinc. In the context of developing effective, low-cost, and environmentally friendly corrosion inhibitors, this study is focused on the action of nontoxic sodium heptanoate of formula CH3(CH2)5COONa, noted NaC7, on zinc corrosion. Electrochemical measurements have shown that the formation of the protective film is dependent on the heptanoate concentration and creates an efficient barrier against aggressive anions. According to investigations on the surface film, the protective material is a layered zinc hydroxyheptanoate Zn5(CH3(CH2)5COO)2(OH)8. Subsequent powder synthesis, thermogravimetric, and powder XRD analysis allowed us to prop...