ABSTRACT
Metallic zinc coatings provide corrosion protection for steel by acting first as a barrier coating and secondly as a sacrificial anode. Whether exposed to the atmosphere or embedded in concrete, if the coating is scratched or compromised in any way, the zinc will still provide galvanic protection to the steel. In the same way, concrete structures reinforced with plain or bare steel showing signs of distress can be galvanically protected with external zinc anodes. Thermal sprayed metallic zinc on the exposed surface of the concrete can be electrically connected to the steel reinforcement and provide corrosion protection to the steel. The external zinc anode will corrode instead of the steel reinforcement, reducing formation of corrosion products which stress and degrade the concrete. Thermal sprayed zinc coatings were used as anodes in ICCP systems on the historic reinforced concrete Cape Creek Bridge, Yaquina Bay Bridge and Depoe Bay Bridge on US Route 101 in Oregon. The 20-plus-year performance confirms that the service life of reinforced concrete structures can be significantly and economically extended by using metallic zinc anodes to protect the plain steel reinforcement from further corrosion.
