Abstract
Arc sprayed zinc and zinc alloy coatings have been used increasingly as galvanic anode systems for cathodic protection of steel reinforcements in concrete structures. This paper discusses the characteristics of the metallic arc sprayed coating-concrete interfacial zone with time at target relative humidities of 25, 60, 85 and 100 percent and ambient temperature. Laboratory experiments were performed upon a series of 25 x 25 x 7.6 cm thick concrete test slabs, which were admixed with chloride concentrations of 0, 3.0, 5.9, and 11.9 kg/m3. The top surface of each slab was sprayed with either pure zinc or a 72 Zn-28 Al (weight percent) alloy to a thickness of 380 micrometer (15 mils). Electrochemical Impedance Spectroscopy (EIS) and conventional electrochemical properties such as galvanic current, resistance and polarization resistance of the anode were routinely measured. The results indicate that relative humidity had an important effect on these parameters and that resistance across the coating-concrete interface was particularly influential with regard to performance of the coating as a galvanic anode.
