A Study On A Corrosion Inhibitor For Sulfuric Acid With High Salt Content At High Temperatures

Acidification is a common technology which is often used in the industrial productionprocess. For example, in order to reduce the corrosion caused by acidity of crude oil, andimprove the quality of crude oil itself, new technology about removing naphthenic acid insitu has caused much attention. During this process, oilfield wastewater is often used todilute concentrated sulfuric acid which accompany with intense heat emission and result inthe formation of a high temperature and high salt content environment which is extremelycorrosive. Therefore, there is an urgent need for study on corrosion protection of stainlesssteel in such a concentrated sulfuric acid environment with high temperature and saltcontent.A local high-temperature and high-salt intermediate sulfuric acid environment willformed in the pipeline in the process of refining naphthenic acid, We studied the influenceof salt and temperature on the corrosion behavior of pipeline materials including mainsubstrate (316stainless steel) and other high-quality steel materials, The corrosionbehaviors in sulfuric acid environment were measured with electrochemical method andweight loss method. We evaluated the inhibition performance of all kinds of singleinhibitors and commercial ones in a typical environmental. According to the comparisonexperiments, we have synthesized a series of inhibitors which contained the maincomponent (quaternary ammonium salt) and other effective assistants. We obtained threekinds of recipes after measuring the inhibition performances of the synthesized inhibitors indifferent environment. The main conclusion of this paper are asinclude the followings:(1)The effect of chloride-containing salt on corrosion behavior of316stainless steelin sulfuric acid solution. We studied the effect of chloride-containing component on thecorrosion behavior of316stainless steel with electrochemical measurements and weightloss method in sulfuric acid solution with different concentration (10-60wt%). The resultsrevealed that the chloride-containing component retard the corrosion with differentefficiency.(2) The establishment of inhibitor recipe. We synthesized a series of quaternaryammonium salts inhibitors by using organic ammines, organic acid, quinolone a nd pyridine. We screened the synthesized single inhibitors and commercial ones according to theirinhibition efficiency on316stainless steel in the above environment.. And we found thatthe inhibition performance of quaternary ammonium salts were much be tter than othertypes of inhibitors. While combined with acetylenic alcohols, the inhibition efficiencieswere generally higher than95%.(3)The effect of salt component and sulfuric acid concentration on inhibition efficiency.We measured the inhibition efficiency of different inhibitors in various concentrations ofsulfuric acid and salt. And we found out that the combination of thioureido imidazolinequaternary ammonium salt with propargyl alcohol exhibited better inhibition effect thanothers in a wide concentration range of sulfuric acid and salts.(4) The application of high-quality steel in sulfuric acid solution with high temperatureand high concentration of salts. We studied the corrosion behavior of high-quality steel(254smo) with weight loss method and then found out that the combination of inhibitorsexhibited the highest inhibition efficiency.