Causes of corrosion in industrial wastewater equipment and pipelines, as well as anti-corrosion measures

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1. Oilfield production and water injection tanks and pipelines, as well as the sewage tanks, vessels, and pipelines in the wastewater treatment plants of refineries, are all 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 number 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 equipment 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 as a result of their reaction with H2S, namely NH4HS and (NH4)2S, are highly corrosive ； 4. Phenolic corrosion agents can damage the coating, exacerbating corrosion. 3. Design of anti-corrosion coatings: Practical applications have shown that conventional coatings (ordinary epoxy paint, epoxy coal tar pitch coating, epoxy phenolic paint, polyurethane paint, chlorosulfonated coating, high-chlorinated polyethylene coating, acid-resistant panels made of epoxy and furan cement, unsaturated polyester fiberglass, and epoxy vinyl ester fiberglass) fail to meet the required standards; within less than a year, they often suffer from color change, delamination, and peeling. In contrast, vinyl resin coatings, epoxy glass flake coatings, epoxy furan coatings, epoxy fiberglass, and epoxy polysulfide rubber coatings have proven to be very effective in practical applications, and their use should be promoted!