Sodium polysulfide corrosion inhibitor
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For HCN corrosion in hydrogenation units, sodium polysulfide corrosion inhibitors are required. Where does this type of corrosion occur primarily, and what is the mechanism of inhibition?
Primarily in heat exchangers and air-cooling areas, the reaction of polysulfides with cyanides can produce thiocyanates. Additionally, polysulfides can inhibit sulfur-induced corrosion of steel through ammonium polysulfide, which achieves this by altering the adhesion and composition of the corrosion products of iron sulfide. Therefore, the injection of polysulfides can reduce corrosion. Typically, polysulfides are introduced into the system by injecting them into the reaction water. Polysulfides cannot stop pitting inside blocked pipes, but they reduce scale buildup; when the system remains clean, injecting polysulfides can minimize blockages and corrosion. This post was last edited by qlasd on 2009-4-8 20:50.]
Sodium polysulfide was a corrosion inhibitor used a long time ago; it is now hardly used at all. Although it has a good corrosion-inhibiting effect on cyanides, its effect on other chlorides and sulfides is very low. Especially in hydrocracking units, the sulfur content is very high; under such conditions, the corrosion-inhibiting effect of sulfides is virtually none, and there is a high likelihood of scale formation due to FeS, while cyanides are present in low amounts. It is recommended to use new types of corrosion inhibitors – I have used Nalco’s EC1009A, and it works well.