Rate of corrosion, extent and nature of microfouling of copper, cupronickel 70/30 and cupronickel 90/10 have been studied for three different seasons at a station on the west coast of India. The corrosion rates for all the three materials are higher during premonsoon as compared to other two seasons. Decreasing trend in the corrosion rate has been observed with increased nickel content. The microfouling assemblage which is estimated in terms of diatoms and bacterial count and their exopolysaccharide exhibited inverse relationship with corrosion rate. Marked seasonal variations in the extent of corrosion and microfouling are evident. The resistivity of copper and its alloys towards microfouling has been found to be in the order as Cu > Cu-Ni 90/10 > Cu-Ni 70/30. X-ray diffraction analysis of the corrosion products revealed the presence of Cu2O as major component in both the alloys.