Accelerated Atmospheric Corrosion Of Copper And Copper Alloys

Abstract

The corrosion behaviour of a range of readily available commercial copper based alloys was examined in three accelerated atmospheric corrosion tests: acidified salt spray, neutral salt spray at 80°C, and the GM (salt spray with thermal cycling) test. The samples exposed to the GM test evinced very little corrosion. During exposure, the weight of all the samples fluctuated in a random fashion, indicating that the corrosion products were only partially adherent and became detached from the surface at random times. The sequence of corrosion product formation on the specimen surfaces during exposure to the neutral salt spray test was very similar to that observed on coppers exposed to the atmosphere, indicating that this test can be used to give accelerated indications concerning atmospheric corrosion in humid marine regions. Four 24 h cycles of salt spray exposure are approximately equivalent to 1 year's exposure to the atmosphere. Alloying copper with phosphorus, tin, zinc, or silicon does not improve atmospheric corrosion resistance. The alloy containing 30%Zn exhibited dezincijication. The nickel silvers exbibited corrosion rates in the neutral salt spray at 80°C that were lower by a factor of at least 13 than those of the high purity coppers. For six of the alloys studied, the as received surface condition correlated with a slightly, but statistically significantly, higher corrosion rate, attributed to residual contaminants from rolling.