Abstract
Thermally sprayed aluminium (TSA) is not immune to corrosion when polarized by sacrificial aluminium anodes. However, the corrosion rate is usually rather low due to a protecting surface oxide on the TSA, keeping the TSA passive. A certain cathodic reaction rate is found on the TSA, producing hydroxide. This hydroxide is a potential threat to the TSA, since aluminium is not passive in alkaline environments. When the TSA is exposed to seawater the hydroxide may be transported away from the TSA surface by diffusion and convection, and the pH is maintained within the passive range. However, in mud there is no convection and the diffusion is limited. This may result in accumulation of hydroxide at the TSA-mud interface and activation of the TSA. The cathodic polarization may therefore result in decreased lifetime of the TSA in mud. The paper discusses corrosion rate of TSA as function of cathodic polarization and temperature, when exposed in subsea mud.