Properties of Salicylidene-Aniline as a Corrosion Inhibitor in Oil and Petroleum Products Transportation Systems

Abstract

Introduction. Risks of accidents and fires during transportation and pumping of oil and petroleum products is a significant problem of technosphere safety. The reasons may be leaks due to corrosion damage to pipelines, tanks and oil storage tanks. In view of the possible serious financial, environmental and social consequences of such incidents, it is important to constantly seek new, more effective approaches to preventing corrosion processes. It is obvious, for example, that at present not all chemical compounds capable of suppressing or inhibiting the destruction of metals and alloys have been thoroughly studied. The presented scientific work is partly aimed at overcoming the lack of data in this area. The objective is to investigate an insufficiently studied compound salicylidene-aniline, which can be a corrosion inhibitor similar to other nitrogen-containing compounds similar in structure and composition.Materials and Methods. The gravimetric method was used to study the inhibitory, adsorption and complexing properties of salicylidene-aniline. The experiments were carried out with St3 steel plates. The mass of metal samples without an inhibitor and with an inhibitor was recorded before and after exposure in the test media. The effect was determined by the change in the corrosion rate. When setting up experiments, the authors were guided by GOST 9.905–82 "Unified system of corrosion and ageing protection. Corrosion test methods. General requirements". The volume of the corrosive medium was determined according to GOST 9.506–87 "Unified system of corrosion and ageing protection. Corrosion inhibitors of metals in water-petroleum media. Methods of protective ability evaluation". The corrosion criteria were taken from GOST 9.908–85 "Unified system of corrosion and ageing protection. Metals and alloys. Methods for determination of corrosion and corrosion resistance indices". The calculations were based on the valuation principle, which sets the ratio of a multiplicative metrized linear order on a set of particular criteria. An integral indicator based on mathematical and methodological approaches was used for ranking.Results. The effect of hydrochloric acid medium on steel samples St3 was studied. Four concentrations of the inhibitor were taken: 0 %, 0.01 %, 0.1 %, and 0.2 %. The mass of metal samples without an inhibitor and with an inhibitor was recorded before and after exposure in the test media. The effect was determined by the change in the corrosion rate. The mass index of corrosion was calculated. The surface quality during destruction and corrosion inhibition was determined in five stages: the elements to be evaluated were selected, the purpose of the evaluation was formulated, the elements of the technical condition of the object under study were found, the essence of determining the usefulness or value of the criterion was described, and the essence of optimization was explained. The studied properties were ranked with respect to the multiplicative metrized linear order on a set of particular criteria. For the calculations, the task was set — to determine the components of vector B in accordance with one of the evaluation stages. We are talking about the stage when the usefulness or value of the criterion is analyzed by points on the numerical axis indicating the state of the object "better — worse". We constructed an indicator z approximating a known or specified (learning) matrix of paired relationships between objects. The resulting indicator allowed us to assess the technical condition of the surface during the course of corrosion and when it slowed down due to the addition of salicylidene-aniline. The result was obtained for samples with a surface area from 10.1∙10-4 m2 to 11.9∙10-4 m2. During the experiment, the mass of the metal decreased by 0.2–0.8 times with the inhibitor and almost by 3.5 times without it. The mass index of corrosion was recorded from 0.15 g/m2∙h to 0.48 g/m2∙h. At the same time, the protective ability of the inhibitor was quite high: the minimum was 77.4 %, the maximum was 94.8 %. This is a convincing indicator. It is also worth mentioning such an advantage of salicylidene-aniline as a low danger. Its hazard class is III (for comparison: the hazard class of aniline is a level higher — II).Discussion and Conclusion. The authors propose to use salicylidene-aniline as a means to increase the safe service life of oil pipelines and tanks. The potential of this composition as an effective corrosion inhibitor, highly soluble in oil and petroleum products, has been proven. Such properties of salicylidene-aniline as slow oxidation and moderate toxicity are noted.