Influence of temperature on corrosion product film formation on CuNi10Fe in the low temperature range: Part 2: Studies on corrosion product film formation and properties in relation to microstructure and iron content

Earlier experiments have shown sea water temperature to exercise a strong. influence on the corrosion behaviour of CuNi10Fe alloys. Investigations attempting to correlate the corrosion product layer properties, and hence the corrosion rate, with microstructural effects are described. Alloy iron content and heat treatment were varied, exposure being carried out at 20 and 40°C under conditions promoting uniform attack. During short term exposure, microstructure was found to have a pronounced influence. On the homogeneous and continuous precipitate containing alloys, good protective corrosion product layers were formed quickly at the higher temperature. The effect of iron content was most pronounced in the alloys containing continuous precipitates. At 20°C, microstructural effects appear to dominate those of iron content. In the long term, however, these effects tended to diminish, all these alloys showing very low corrosion rates under the present test conditions. The discontinuous precipitate containing alloys did not pelform as well, owing to the formation of a less protective corrosion product layer.