Corrosion and Protection of Sulfur-Containing Wastewater in the Petrochemical Industry

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1. Sewage tanks, vessels, pipes, etc. in the petrochemical industry are severely corroded by sulfur-containing wastewater. Since the wastewater contains large amounts of H2S, NH3, HCN, and CO2, as well as numerous harmful ions such as Cl- and SO42-, along with a high concentration of bacteria, and the temperature is as high as 70–80 degrees Celsius; in some cases, phenolic corrosive substances are also present. Therefore, if no effective anti-corrosion measures are taken, corrosion of these devices will be quite severe, leading to phenomena such as thinning of the carbon steel layer, local perforations, bubbling, cracking, and stress corrosion cracking in the welds, which can quickly result in the destruction of the equipment! 2. Analysis of corrosion causes: Different crude oils and production processes result in varying corrosive agents in the wastewater; as a result, the causes and mechanisms of corrosion differ to some extent. Generally speaking, however, the following points apply: 1. Corrosive agents such as H2S, NH3, and HCN present in sulfur-containing wastewater cause corrosion due to electrochemical reactions that generate H2S ； 2. Hydrogen embrittlement corrosion caused by hydrogen atom penetration ； 3. The wastewater contains large amounts of NH3, CN-, and Cl-. The substances formed upon reaction with H2S, namely NH4HS and (NH4)2S, are highly corrosive ； 4. Phenolic corrosive media can damage the coating, thereby exacerbating corrosion. 3. Design of anti-corrosion coatings: Practical applications have shown that conventional coatings (ordinary epoxy paints, epoxy coal tar pitch coatings, epoxy phenolic paints, polyurethane paints, chlorosulfonated coatings, high-chlorinated polyethylene coatings, acid-resistant boards made of epoxy and furan mortars, unsaturated polyester fiberglass, and epoxy vinyl ester fiberglass) fail to meet the required performance standards. Within a year, issues such as color change, delamination, and peeling often occur. In contrast, vinyl resin coatings, epoxy glass flake coatings, epoxy furan coatings, epoxy fiberglass, and epoxy polysulfide rubber coatings have proven to be highly effective in actual use by various organizations; therefore, they can be widely adopted!