The corrosion of architectural aluminum alloy under Antarctic conditions

In 1968, a ten year programme to assess the behaviour of anodised aluminium in the atmosphere was started. This consisted of exposing a range of test coupons at 5 sites in and around Christchurch and testing coupons from the same series in an accelerated corrosion environment in the laboratory. The programme was extended to consider the implications of atmospheric temperature extremes. This led to the provision of a test stie in Lae, Papua New Guinea and one at Scott Base in Antarctica. These sites provided the extremes of hot humid climate and a cold, pollution free environment. In 1974 it was discovered that the Scott Base site was unsatisfactory as the corrosion test coupons were exposed adjacent to a maze of chimneys with attendant pollution. A pollution free site was then made available at Arrival Heights. The Christchurch programme was reported in 1980 after the coupons had been exposed for a total of 12 years. This was followed in 1983 with a further report covering the results obtained from the remaining New Zealand sites. In 1985 the results of the Antarctic corrosion was reported. There are two manufacturers of architectural aluminium alloy and coupons were obtained from extruded stock provided by these manufacturers. Three thicknesses of anodic coating were initially specified and the anodising was done by standard commercial techniques at a reputable plant in Christchurch. Each condition was duplicated and exposed with unanodised coupons in a low cost rack at each of the sites chosen.The racks were annually inspected with washing and weighing to measure weight changes. Accelerated corrosion tests were carried out on identical coupons to those used in the atmospheric programme in a salt mist environmental chamber.