Title: Sacrificial Cathodic Protection of RC & Prestressed Structures - Thermally Sprayed Aluminium Alloy

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Publication: CIA

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Date: 2/13/2011

Abstract:
An intensive research and development program was funded by the United States Federal Highway Administration (FHWA) in 1994 to develop new sacrificial anode materials for cathodic protection of reinforced and prestressed concrete bridge substructures. As part of this research effort a new galvanic anode was developed for corrosion control. The study identified an Aluminum-Zinc-Indium (Al-Zn-In) alloy that is capable of providing improved cathodic protection to steel embedded in chloride contaminated concrete. The anode is applied to concrete structures using electric arc spray equipment to form a galvanic coating. The anode has demonstrated in both field and laboratory testing to provide a degree of cathodic protection that is superior to thermally sprayed zinc. Several installations have been completed in marine environments. In these installations the thermal spray contractors realized a production rate of 10-15 m2 per hour. High bond strength was evident, and the level of protection on the reinforcing steel exceeded the 100-mV polarization development criterion for cathodic protection of steel-in-concrete. Since the anode is a galvanic system, no monitoring or maintenance is required. Visually the anode coating has a grey-silver color similar to concrete. Based on predicted consumption rates the aluminum alloy can be expected to provide a reasonable life expectancy of 10-15 years before touch-up reapplication is required.