Anti-corrosion and thermal insulation solutions for petrochemical storage tanks

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The petrochemical industry is a complex and large-scale industrial system, with towers, furnaces, tanks, vats, and pipelines being the basic components of petrochemical plants. The petrochemical processing processes are characterized by their high degree of continuity and complexity. The corrosion environments and types they face are diverse, including electrochemical corrosion, chemical corrosion, erosion wear, atmospheric corrosion, soil corrosion, seawater corrosion, and high-temperature corrosion. This plan focuses on the anti-corrosion protection measures for storage tanks used in the petrochemical industry. For corrosion prevention solutions applicable to other operating conditions, please contact the technical department of Longyuan Naxin Company. Storage tanks are mainly classified by structure into: internal floating roof, arch roof, vertical, horizontal, and spherical tanks ； Classified by purpose, they fall into five categories: crude oil tanks, intermediate product tanks, product tanks, sulfur-containing wastewater tanks, and gas holders. Classified by elevation: above-ground tanks, buried tanks, semi-buried tanks, and elevated tanks. 　　The design of anti-corrosion and insulation coatings for storage tanks shall follow the relevant standards: \"Specifications for Pre-treatment of Steel Surfaces before Painting\" SY/T0407-2012, \"Electrostatic Safety Regulations for Liquid Petroleum Products\" GB/T 13348-2009, \"Insulation Coatings for Petroleum and Chemical Equipment\" HG/T5182-2017, \"Technical Specifications for Anti-corrosion Engineering of Steel Petroleum Storage Tanks\" GB/T50393-2017, \"Design Specifications for Anti-corrosion Coatings on Petroleum and Chemical Equipment and Pipelines\" SH/T3022-2011, as well as \"Paints and Varnishes – Corrosion Protection of Steel Structures by Protective Coating Systems\" and the classification of corrosive environments per ISO12944-2. Recommended solutions for anti-corrosion coatings on the inner walls of storage tanks: The anti-corrosion protection scheme for the inner walls of storage tanks is designed and selected based on factors such as the type of tank, the medium stored, temperature, and pressure. The coatings chosen should possess good resistance to corrosion, resistance to solvent immersion, and resistance to chemical exposure ； It is required that when the coating is immersed in the medium for an extended period of time, the paint film shows no changes, does not bubble, does not swell, does not peel off, and does not contaminate the storage medium. Consideration should also be given to heavy oil and wastewater tanks, equipped with heaters or other means for heating, in order to address the changes in the coating’s temperature resistance and aging resistance as a result of such heating. Tank type | Coating structure | Paint name | Number of coats | Dry film thickness
Heavy oil tank | One bottom coat | Polymer acid-alkali resistant anti-corrosion paint | 2 | 2000 μm
| Two bottom coats | Inorganic zinc-rich heavy anti-corrosion paint | 2 | 2100 μm
| Primer | Polymer acid-alkali resistant anti-corrosion paint | 1 | 1100 μm
| Topcoat | Polymer conductive anti-corrosion paint | 1 | 1100 μm
Technical advantages: Option 1: The coating forms a dense film; after curing, it has a high degree of cross-linking, providing resistance to penetration corrosion by sulfides and chloride ions ； Excellent high-temperature resistance ； It provides excellent corrosion protection at the oil-water interface and at the bottom of the tank. 　Option 2: A metal-based static-dissipative coating with good resistance to electrochemical corrosion and temperature. 　Option 3: Builds on Option 1 by adding antistatic properties to the coating, and can be used for aviation kerosene tanks. For lightweight oil tanks: 2100 μm of inorganic zinc-rich heavy-duty anti-corrosion coating on the first bottom surface; epoxy heavy-duty anti-corrosion coating/polymer acid- and alkali-resistant anti-corrosion coating of 2–3160–240 μm on the second bottom surface. Technical advantages: Option 1 offers excellent resistance to electrochemical corrosion, static electricity dissipation, and temperature fluctuations. 　Option 2: The coating forms a dense film; after curing, it has a high degree of cross-linking, providing resistance to penetration corrosion by sulfides and chloride ions. For sewage and oily waste storage tanks containing acids, alkalis, sulfides, etc.: First primer – acid- and alkali-resistant anti-corrosion coating, 180μm; top coat – polymer-based acid- and alkali-resistant anti-corrosion coating, 180μm; second primer – acid- and alkali-resistant anti-corrosion coating, 180μm; intermediate coat – polymer-based acid- and alkali-resistant anti-corrosion coating, 2120μm; top coat – polytetrafluoroethylene-based acid-resistant high-performance anti-corrosion coating, 160μm. Technical advantages: Special anti-corrosion coatings with excellent acid- and alkali-resistance are used, making them suitable for use in environments exposed to highly oxidizing acids ； Ultra-fine flaky fillers enhance the impermeability of the coating system ； The coating system possesses high-temperature and humid heat resistance ； Option 2 is an upgraded version with superior corrosion resistance, as well as better self-cleaning and anti-staining properties. 　Recommended solutions for anti-corrosion and insulation coatings on the outer wall of storage tanks. Outer wall of storage tanks: The outer wall of storage tanks is primarily subject to corrosion caused by the atmospheric environment, including moisture, oxygen, temperature fluctuations, coastal salt mist, corrosive gases such as those found in chemical industries, as well as UV radiation that leads to the degradation of the coating. For storage tanks located in areas with heavy wind and sand, the wind and sand can cause mechanical wear to the tank’s surface coating. Corrosion beneath the insulation layer: In crude oil storage tanks and heavy oil storage tanks, the insulation layers (such as polyurethane foam, vermiculite, sepiolite, glass wool, rock wool, etc.) contain large amounts of soluble salts and Cl-. The water that penetrates from the outside, along with the condensation water that forms inside, is acidic in nature ； The corrosion rate can exceed 0.8 mm/a ； Water flows down along the tank walls, causing electrochemical corrosion and chemical corrosion due to the oxygen concentration gradient at the lower part of those walls.