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How to Improve corrosion resistance of shipbuilding steel?

Posted: 9/4/2011 11:33:23 PM

Improved corrosion resistance is also an important factor in ensuring security. Research shows that high age of the ship boat damage is generally caused by corrosion loss. Corrosion is the material result of the interaction with the environment, particularly by the type of goods and construction and transportation environments and other complex factors. In many cases, the ship's internal environment, the corrosion phenomenon has not technically been clear. According to several studies, the rear deck of the ship yard of the Ministry of corrosion loss is actually due to hydrogen sulfide gas and crude oil in the explosion-proof gas containing water vapor, oxygen, carbon dioxide as a result of diurnal temperature changes due to alternating wet and dry, the actual situation is more mild corrosion, the corrosion rate of about 0.1 mm / year. In addition, because a lot of sludge and corrosion products on the site of misunderstanding caused some problems. Then, clearly this fact is due to oil sludge in the precipitation of solid sulfur containing hydrogen sulfide generated.
On the other hand, the bottom of the corrosion occurred, such as the maximum of 4 mm / year rate of occurrence of localized corrosion, and the recent emergence of dual-chamber (DH) and so has become a significant problem. Crude oil tank (COT) to form a thick bottom layer of oil covering, oil-covered steel this is not easy to corrosion. However, due to crude oil tankers regularly use COT internal high-pressure crude oil washing, which damage the oil coating. In particular, because the bottom of the COT, DH floor directly due to high crude oil Department of erosion resulting from the injury site more can be expected, there will be significant corrosion occurred. In addition, COT in crude oil, because oil wells in the presence of high concentrations of dissolved rock salt and mixed with groundwater, these rock salt precipitation in crude oil after the process remain in the bottom of a main floor of the Ministry of corrosion.
To the research-based, in the form of corrosion-resistant steel components of a variety of results, which expand the crude oil storage tank with corrosion-resistant steel varieties. This corrosion-resistant steel used in the actual ship on the results publicly. 300,000 dwt VLCC for the COT floor all in all 15 tanks and six tanks in the house was used without coating. 2 to 3 years after the voyage that, with the need to repair more traditional steel 4 mm to 10 mm deep localized corrosion pits than this use of corrosion-resistant steel in no apparent need to repair some of the local corrosion. According to other studies, can be assumed that, during the life of the entire ship's age, without the need for steel repair. In addition, the steel also for the development of new corrosion-resistant steel used in the actual ship. Can be expected, corrosion-resistant steel will gradually become clear advantages for various applications.
Corrosion response of the ship was adopted at the IMO, and is gradually standardized. Last year, the ballast tank coating standard has been approved. In addition, the mandatory tanker crude oil storage tank painting also being discussed. Along with the tanker corrosion-related technology options increase, if the application of corrosion-resistant steel is possible, then improve shipbuilding productivity, reduce costs and reduce environmental pressures may be achieved.