Evaluation of naphthenic acidity number and temperature on the corrosion behavior of stainless steels by using Electrochemical Noise technique

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• 作者：Fernanda Hass^a ; Ana C.T.G. Abrantes^a ; Alysson N. Dió ; genes^a ; ^b ; ^{diogenes@up.com.br" class="auth_mail} ; ^{andiogenes@yahoo.com.br" class="auth_mail} ; Haroldo A. Ponte^a
• 关键词：Electrochemical Noise ; Corrosion ; Naphthenic acids ; Petroleum refining
• 刊名：Electrochimica Acta
• 出版年：1 April, 2014
• 年：2014
• 卷：124
• 期：Complete
• 页码：206-210
• 全文大小：2012 K

文摘

The processing of heavy oils in Brazilian refineries has exposed the equipment to more severe corrosive processes, mainly due to the presence of contaminants. The naphthenic acids can be quoted as an example of these contaminants, which are made of organic acids saturated rings and one or more carboxylic groups. Consequently, refiners are adjusting their metallurgy facilities and investing in real time instrumentation for monitoring the corrosion rates, thus enabling the optimization of the consumption of opportunity crude oils and dosing of anti-corrosive products. As an alternative to commonly used techniques for corrosion monitoring, such as weight loss coupons and electrical resistance probes, studies are being conducted to evaluate and validate the use of the Electrochemical Noise technique in oily media. This method has proven to be the most appropriate for high ionic strength solutions, as the case of oil, corrosive and it is proven to be sensitive for corrosion processes caused by naphthenic acids. This study aims to evaluate the influence of temperature - 25 掳C, 65 掳C and 120 掳C - and the total acidity number (TAN) - 0.5, 1.5 and 2.5 mg KOH/g - in the naphthenic acid corrosion in austenitic stainless steel type 316. An electrochemical reactor consisting of three identical electrodes of 316 stainless steels roads, with an area of 8.95 cm² for each electrode, was used to evaluate the corrosive process, along with electrolytes consisting of pure mineral oil and mineral oil with naphthenic acids. The Electrochemical Noise technique was applied in the first 5 h of contact between the electrodes and the electrolyte, with a frequency of 10 Hz acquisition. As a result, it was observed that when the temperature or the TAN increase, both the susceptibility of the 316 steel to general corrosion and the incidence of localized corrosion also increase. Meanwhile, the temperature effect was more significant in the studied conditions. Besides, the Electrochemical Noise technique demonstrated sensitivity to identify corrosive process variations even in conditions considered to be of very low severity.