Storage tanks are an important object in the technological chain of the processes of extraction, transport, and processing crude oil and gas condensate. The planned service life of the storage tanks is 20--40 years. However, in a number of cases, failures of storage tanks, associated with corrosion, are already detected after 1.5-2.5 years in service. According to the data of the American Petroleum Institute, approximately 19% of all leakage of hydrocarbon products is caused by corrosion damage in storage tanks [ 1]. It is therefore important to examine the existing storage tanks, and carry out the justified selection of the method of technical diagnostics and organization of diagnostic technology. Inspection of the storage tanks and recommendations, developed on the basis of the inspection results, should guarantee failure-free operation of the container up to the next inspection. At the same time, the frequency of inspection and the methods of diagnostics used for this purpose must be economically justified and have no influence on operating expenditure, i.e. the frequency of inspection and also the required sensitivity of the diagnostics devices, used in inspection, should not be too high. This can be achieved as a result of the careful analysis of the main reasons for premature failure of storage tanks and the data on the nature and intensity of damage.It is well-known that corrosion is one of the main reasons for failures of storage tanks [2]. Depending on the phase and chemical composition of the working product, service temperature, the system of anticorrosion measures, climatic conditions, etc, corrosion failure can take place on both the internal and external surface of the storage tank. In most cases, corrosion damage develops most rapidly from inside at the lower belt (the interface between well water and liquid hydrocarbons) and the dished end under the effect of well water (corrosion rate -0.4-4).6 mm/year), and also in the upper belt (phase boundary between the liquid hydrocarbons and the gas-air mixture) and the roof under the effect of the water condensate, atmospheric oxygen, and acid gases (corrosion rate -0.4 mrn/year). Corrosion damage is usually of the crevice type. Sometimes, when storing products with a high hydrogen sulfide content, corrosion cracking and hydrogen delamination is observed in components of the systems. However, crevice corrosion takes place most frequently, and in the currently valid standard documents for the inspection of storage tank corrosion failure is usually represented by this type of damage.The main devices for inspecting the development of corrosion damage are thickness gauges. The currently valid Russian standard documents specify that when examining the storage tanks to determine the wall thickness and detect the rate of corrosion failure, it is necessary to use devices with the measurement error not exceeding +0.1 mm [3]. The corrosion state of the internal surface of the storage tank is inspected usually once every 2-5 years. The periods of inspection are sele...

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Test results are given from using railroad tank cars with tanks made of AD0 aluminum and intended for shipping acid mixtures instead of shipping solutions of sodium hydrosulfide. All the tank cars showed through pitting on the bodies in the longitudinal and transverse welded joints. The causes and mechanism of the corrosion have been examined. It is emphasized that it is necessary to consider carefully a medium when tank cars are used not for their original purpose.Quite often, chemicals are shipped in tank cars not intended for transporting them. As a rule, one examines not only the state of the tank cars but also the chemical activity of the load in relation to the material of the body. The tank cars may fail prematurely if a superficial attitude is taken to this analysis.The following is a practical example. Between June 2005 and September 2006, nine railroad tank cars of models 15-1406 with bodies of AD0 aluminum, which are intended for shipping acid mixture, were used for shipping a solution of sodium hydrosulfide (TU 2153(TU -296-00204168-2001. After 13 months of operation, the bodies of all the tank cars showed through pits in the longitudinal and transverse welded joints (Fig. 1).The maker of the sodium hydrosulfide (Volzhskii Orgsintez company) issued a document entitled "Load hazard characteristics," where it is stated that the corrosion rate for aluminum in NaHS solution is not more than 0.2-0.3 mm/yr.As the sheet thickness in the tank car body is not less than 25 mm, the Lukoiltrans company that operates the tank cars considered that it is possible to use them not for their original purpose (without agreement in the established way with the Railroad Operating Corporation and the Russian Industrial Supervision Service).We examine the character of the load to establish the causes of the welded joint failure. Table 1 gives a composition of technical sodium hydrosulfide.The viability of aluminum is substantially dependent on the pH, and as this was not determined promptly, the analysis of the failure causes was begun with the determination of the pH for model solutions. We prepared two solutions.

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