Effect of Type of Surface Treatment and Epoxy Coating on Corrosion Activity


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Title: Effect of Type of Surface Treatment and Epoxy Coating on Corrosion Activity

Author(s): Irina L. Kondratova, Theodore W. Bremner, and Sakir Erdogdu

Publication: Special Publication

Volume: 163


Appears on pages(s): 447-462

Keywords: accelerated tests; chlorides; corrosion; reinforcing steels; underwater structures; Materials Research

Date: 8/1/1996

Presents results of a study on the effect of several types of coatings and surface treatmets on the corrosion activity on specimens containing U-shaped epoxy-coated reinforcing bars cast in concrete slabs. These reinforced concrete slabs were subjected to severe exposure conditions and evaluated after four years. To obtain results in a short time period, a high water-cement ratio of 0.6 and concrete cover of only 20 mm were used. Four different types of epoxy coatings were investigated, with some bars being coated before bending and some coated after bending. The reinforcing steel had been surface treated by the supplier in seven different ways before coating, with some of the bars receiving a primer coating before application of the epoxy coating. Also, the surfaces of some bars were contaminated with salt prior to coating. Some reinforcing steel bars were intentionally damaged with the damaged area being seven 6 mm x 6 mm square spots evenly distributed over the surface of each bar. The exposure conditions were a laboratory test chamber simulating a marine environment and a natural marine environment site at Treat Island, Maine. Assessment of corrosion activity was carried out using linear polarization resistance and open circuit potential techniques. A visual survey was done as well. The results indicated that undamaged epoxy-coated reinforcing steel bars performed very well, with no corrosion occurring after four years of severe exposure conditions with low strength concrete (w/c=0.6) and only 20 mm of cover. The test results indicate that, after four years of exposure, most of the various surface treatments or types of coating were equally effective in terms of long-term corrosion protection of the reinforcing steel. However, the exception was a salt contaminated surface, in which a corrosion rate of up to 50 percent of that for uncoated reinforcing steel was observed.