Recently, welded steel pipes have been used to cooling-water inlet-pipes of turbine condenser in power plants.
So we experimented on various methods of corrosion-protection for these pipes mainly by dipping tests to actual sea water, and obtained following results.
(1) Corrosion rates of carbon steel plates in sea water about 0.18mm/year, and ductile cast irons and low-alloy cast irons showed similar corrosion rates, but the casting skin of these cast irons appears to have no long-time effect on corrosion in sea water.
(2) Zinc coatings were highly resistant in sea water and showed also anti-fouling effects.
(3) Coal-tar enamel and asphaltic enamel coatings may be expected long-time effects for applying to steel structures, but anti-fouling properties were very poor, especially in asphaltic enamel, so chlorination methods should be used in case of these coating applied.
(4) Cathodic protection with impressed currents may be effective for these sea water pipes if accurate design are applied.
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