Corrosion and protection of sulfur-containing wastewater in industrial environments

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Corrosion and Protection of Sulfur-Containing Wastewater in Industrial Environments 1. Corrosion Conditions Equipment, pipelines, wastewater systems, tanks, and pipes in industrial settings are all severely corroded by sulfur-containing wastewater. Due to the presence of large amounts of H2S, NH3, HCN, and CO2 in the wastewater, along with high levels of harmful ions such as Cl- and SO42-, and sometimes temperatures as high as 70–80 degrees Celsius, as well as phenolic corrosive substances, corrosion of these equipment can be quite severe. This leads to phenomena such as reduced thickness of carbon steel, local perforations, bubbling, cracking, and stress corrosion cracking in welds, thereby affecting the equipment’s service life and safe operation. 2. Analysis of corrosion causes: Different media and processing methods result in varying corrosive agents present in wastewater, and while the causes and mechanisms of corrosion differ to some extent, they generally fall into the following categories: ① Corrosive agents such as H2S, NH3, and HCN in sulfur-containing wastewater, which cause corrosion due to electrochemical reactions that generate H2S ； ②Hydrogen embrittlement corrosion caused by hydrogen atom penetration ； ③The 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 ； ④Phenolic corrosion agents can damage the coating, exacerbating corrosion. 3. Corrosion-resistant coating design: Experience has shown that conventional coatings (such as ordinary epoxy paints, epoxy coal tar pitch coatings, epoxy phenolic paints, polyurethane paints, etc.) cannot meet the required standards; within less than a year, they often suffer from color change, delamination, and peeling. In contrast, some polymer alloy coatings, epoxy glass flake coatings, epoxy furan coatings, and epoxy fiberglass materials yield better results in practical applications, and can be used to address equipment corrosion issues.