Efficiency of coatings applied on rebars in concrete

W. MORRIS; M. VAZQUEZ,; S. R. DE SANCHEZ

JOURNAL OF MATERIALS SCIENCE

SPRINGER

Año: 2000 vol. 35 p. 1885 - 1890

0022-2461

The performance of three reinforcing steel bars (rebars) coatings is analyzed by means ofelectrochemical methods. The coatings are representative of those commonly used duringthe repair of concrete structures affected by corrosion in the coastal regions of Argentina:an epoxy rust conversion coating, a zinc-rich epoxy, and a sprayed zinc coating. Twoexposure conditions were investigated: immersed in a saline solution (wet) and exposed toan indoors atmosphere (dry). The rebar corrosion potential (Ecorr), the corrosion rate (CR)and the electrical resistance (R) between bars were measured during approximately 800days. In the dry condition the three coatings presented a satisfactory performancecharacterized by passive Ecorr values and CR values lower than 1 ¹m/year. On the otherhand, the performance of the coatings in the wet condition depended on their formulations.The rust conversion coating showed active Ecorr values and CR values higher than thosemeasured on the uncoated bars. The zinc-rich epoxy and the sprayed zinc coatingspresented Ecorr values typical of active zinc. This indicates a certain degree of cathodicprotection provided to the reinforcing steel. Besides, R values showed that in this condition,coatings do not provide a barrier type of protection.