The corrosion of flat bottom storage tanks has not been historically a serious problem to the petroleum refining industry. This may have to do in par with the fact that most tanks are constructed on elevated granular pads which afford good drainage and also as early as the 1940’s, cathodic protection was being used sporadically for the external and in some cases, internal surfaces. For one or a combination of reasons, tank bottom corrosion has become a concern more recently. Certainly, environmental and safety considerations are more important now than at any other time in the past, and more significantly, much of the existing surface storage tankage has now accumulated considerable age. Whereas piping systems are often abandoned or replaced when refinery or petrochemical plant modifications are made, this is not usually the case for tankage which is commonly retained for future service. Indeed, when a large number of refineries were decommissioned in the early ‘80’s, often the storage tanks were retained for future product storage. There is therefore a general need to make existing storage facilities serve a longer and longer period of time.
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