Comparative studies of the seawater corrosion behaviour of a range of materials

A laboratory investigation has been undertaken to compare the corrosion behaviour of titanium, three stainless steels and a nickel-base alloy in a range of environmental conditions relevant to desalination plant operation. The method of assessment of corrosion was by the use of electrochemical monitoring in the form of anodic potentiodynamic polarisation scans. The effects of seawater salinity (35,000 and 55,000 mg/l total dissolved solids), temperature (25degreesC and 45degreesC) and hydrodynamic conditions were examined. Experiments were conducted in static water, flowing water and severe jet impingement conditions. The comparative corrosion resistances of the materials fell into three groups from the most corrosion resistant, titanium, via a superaustenitic stainless steel and Hastelloy C-276, to the alloys (types 316L and 430 stainless steels) with the lowest corrosion resistance. Flowing seawater at 3 m/s did not represent a significant additional degree of severity in relation to static immersion but the performances of all the materials were degraded, although to different extents, in the jet impingement (95 m/s) conditions. The detailed discussion focuses on the hydrodynamic effects as well as considering the relevance of the findings for materials selection in desalination plant.