Corrosion and Protection of Petrochemical Sewage Tanks (Examples)
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This post was last edited by Wang Wei2 on 2023-12-2 at 10:13. Corrosion and protection of wastewater tanks in the petrochemical industry (examples): The acidic water tanks used in sulfur processing units and acid gas treatment systems are highly corrosive when operating at temperatures between 50–80°C, as the feedwater contains various substances such as H2S, NH3, CO2, CN-, phenols, and oils. For epoxy-based coatings and various other anti-corrosion coatings used inside tanks, the damage is severe; problems arise within less than 3 months of use, such as bulging, hardening of the coating, and cracking. Severe stress corrosion occurs on exposed metal surfaces, causing serious damage to storage tanks; this is a problem in petrochemical systems. The effects of the following materials. ⑴Nanomaterials: Titanium nanopolymer coatings are used as anti-corrosion coatings. Nearly five years of use has proven that the anti-corrosion coating performs very well under these conditions. It overcomes the problem of conventional special anti-corrosion coatings being susceptible to corrosion and unable to withstand high temperatures, filling the gap in domestic solutions for use under such conditions. ⑵Stainless steel: Problems arise from the use of a stainless steel lining; the stainless steel is bonded to the tank body by welding, resulting in an interface layer in between. Using stainless steel as a lining in this type of operation presents the following problems: In sulfur-containing wastewater (under conditions similar to those in oil refineries), the test results for 1Cr18Ni9Ti were as follows (temperature: 80°C ± 5°C, immersion time: 48 hours, pH: 3–4): mass loss of -0.093% per 2 days, or -18.2% per year. Without considering stress corrosion cracking and pitting. In the dosing tanks for refinery wastewater and process water (containing aqueous chemicals, without the harsh conditions of acidic water), 2-mm stainless steel plates developed perforations within less than a year of use, resulting in their disposal.
Wastewater treatment is an important aspect in the petrochemical industry, and wastewater tanks are exposed to highly corrosive substances during this process. In particular, they are confronted with pollutants such as hydrogen sulfide (H2S), ammonia (NH3), carbon dioxide (CO2), cyanides (CN-), phenols, and oils. Coupled with high operating temperatures of 50–80 degrees Celsius, this increases the risk of corrosion. Traditional epoxy-based coatings and various other anti-corrosion coatings may not be able to withstand such a highly corrosive environment; this manifests as blistering, hardening, and cracking of the coatings, with their service life being less than 3 months. The two materials mentioned in the example offer solutions to this problem to varying degrees: 1. Nanomaterials: The use of titanium nanopolymer coatings as anti-corrosion layers enables resistance to environments with high temperatures and strong corrosive agents. Proven through nearly two years of use, it exhibits excellent corrosion resistance, effectively addressing the issue of traditional special anti-corrosion coatings, which are resistant to corrosion but not to high temperatures. 2. Stainless steel: Although stainless steel is an excellent corrosion-resistant material in many environments, its performance is not ideal in the environment of petrochemical wastewater tanks mentioned in the example. Experimental data show that the mass loss of 1Cr18Ni9Ti stainless steel in sulfur-containing wastewater can reach -18.2%/year, without taking into account the risks of stress corrosion cracking and pitting. Additionally, when using a thinner stainless steel sheet (2 mm), perforations occurred within less than a year, rendering it unusable. In summary, regarding the corrosion and protection of petrochemical wastewater tanks, it is crucial to select appropriate anti-corrosion materials. Nanopolymer coatings represent a viable solution due to their excellent corrosion resistance ； Traditional stainless steel materials may not be suitable for such extremely corrosive environments, especially when there is liquid penetration and mechanical stress. When selecting anti-corrosion protection measures, it is necessary to consider the specific chemical composition of the medium, temperature, pH value, and other factors that may affect the corrosion rate. Comprehensive protective measures should be implemented to ensure the safety and service life of sewage tanks. .