バラストタンク耐食鋼適用船の塗装劣化挙動

抄録

Coating deterioration behavior of water ballast tanks in a very large ore carrier using a corrosion resistant steel (CRS) was investigated by analyzing the photographs which the same parts were taken in 4.8 and 7.3 years after shipbuilding. The investigated components were upper decks and edges of upper deck longitudinal members. Coating deterioration from 4.8 to 7.3 years was classified into the growth of single deterioration, combination and new generation. The ratio of new generation on the edge in 7.3 years was less than that on the upper deck, and decreased very much compared to 4.8 years. Deterioration area on the upper deck and deterioration length on the edge of the longitudinal member using the CRS were suppressed to about 40% and 70% of those using a conventional steel, respectively. One dimensional coating deterioration rates of the CRS were reduced to about 70% of those of the conventional steel on the edge part of the longitudinal member and the upper deck. This ratio of the CRS to the conventional steel in the hull components agrees with those in a laboratory corrosion test and an onboard doubling plate test. From the change of coating deterioration length on the edge until 7.3 years, the average recoating life with the CRS is considered to be 25 years or more.