Various polymeric coatings have been exposed to natural saltwater environments in Buzzard' s Bay, MA and at La Costa Island, FL for the last 18 years and 21 years respectively. The coating systems were applied to 8 inch (20.32 cm) by 8 inch (20.32 cm) by 40 feet (12.19 m) A36 steel "H" pilings. The depth of the water ranged from 4 feet (1.22 m) to 8 feet (2.44 m). Periodic visual inspections have been conducted to evaluate the performance of the coating/ primer systems in the splash zone and in the immersed zone. The coatings had windows to evaluate the under film corrosion attack by saltwater present near the Cape Cod canal. The coatings were evaluated according to ASTM visual standards at low tide. Results of the coating inspections and an evaluation of their effectiveness in preventing the corrosion of steel pilings in seawater will be presented.
This report assesses (1) the rate of corrosion of bare steel with and without cathodic protection, and (2) the effectiveness of various commercially avail able coating systems in preventing corrosion of steel piles in seawater. Eighteen coatings and four sacrificial anodes were tested on 24 sets (three piles per set) of ASTM A 36 or ASTM 690 steel H-piles exposed for 5 years at Buzzards Bay, Massachusetts. Performance ratings were established for the following coatings: organic, organic over metal-filled, organic over metal filled with cathodic protection, metallic organic over metallic, and organic with cathodic protection. It is concluded that sacrificial anodes of zinc and aluminum effectively reduced the corrosion rate of bare carbon steel (ASTM 36) piles in the immersed zone from 0.076-0.102 mm/yr (3-4 mils/yr) to zero, and the coating performing best was coal tar epoxy over zinc-rich primer.