How to properly apply anti-corrosion coating to the outer wall of in-use LNG storage tanks?

It should be over 6 years, like those manufacturers that handle anti-corrosion treatment for ships

For the anti-corrosion coating of the outer wall of LNG storage tanks, the following techniques can be employed to improve the quality of the work and extend its service life: 1. High-performance coatings: Use high-performance coatings with excellent corrosion resistance for painting, such as polyurethane coatings and epoxy coatings. These coatings possess excellent weather resistance and chemical corrosion resistance, enabling effective protection of the outer walls of storage tanks. 2. Surface treatment: Before painting, the metal surface needs to be thoroughly prepared, including rust removal, cleaning, and polishing. Methods such as mechanical rust removal and spray rust removal can be employed to ensure that the metal surface is smooth and free of impurities, so that the paint can adhere firmly. 3. Explosion-proof design: Given that LNG, petroleum, and natural gas fall under Class 1 fire and explosion hazard areas, strict explosion-proof requirements must be followed during construction. Flame-free tools and equipment can be used for metal surface treatment and painting to ensure safety. 4. Regular inspection and maintenance: After coating is applied, it is necessary to regularly check the condition of the coating and carry out repairs and maintenance as needed. If damage or corrosion is detected on the coating, it needs to be addressed promptly to ensure its functionality and performance. In summary, by selecting appropriate high-performance coatings, carrying out thorough surface treatment, complying with explosion-proof requirements, and performing regular inspections and maintenance, effective anti-corrosion coating of the outer walls of LNG storage tanks can be achieved to extend their service life. .

This post was last edited by Wang Wei2 on 2023-8-5 at 11:41. Polyurethane coatings, epoxy coatings, etc. are chosen as they possess corrosion resistance and meet the design requirements. However, these conventional materials require a metal surface treatment of grade Sa2.5, which poses no problem for the construction of new storage tanks. The key issue is that for LNG storage tanks in use that require secondary painting, sandblasting of the metal surface (dry sandblasting or wet sandblasting) cannot be used when fire and explosion prevention measures are required at the site. If the metal surface does not reach the Sa2.5 grade, the quality of the coating applied will not meet the requirements, and its service life will be only 1 to 2 years; therefore, materials of the polyurethane or epoxy coating type cannot be used in such cases. As for using other manual or mechanical methods for rust removal, one issue is that the efficiency is low ； Secondly, it also fails to reach the Sa2.5 grade. As shown in the figure below, during the second coating process, sparking is not allowed during the metal surface treatment. Therefore, given the special circumstances of the secondary coating of LNG storage tanks, solutions can be explored by considering the properties of anti-corrosion coatings, such as using anti-corrosion coatings with low surface treatment for corrosion protection.

For LNG storage tanks that are in use and require secondary coating, given the on-site fire and explosion prevention requirements as well as the fact that the metal surface does not meet the standards required for conventional anti-corrosion coatings, special anti-corrosion coatings with reduced surface treatment can be considered for corrosion protection. These special coatings possess excellent corrosion resistance and are suitable for situations where metal surface treatment is difficult. A viable option is to use spray-on anti-corrosion coatings such as iron red and iron black; these coatings require no mechanical rust removal, only the removal of loose corrosion products and dust. This coating possesses excellent adhesion and weather resistance, enabling it to effectively protect the outer wall of storage tanks. Another option is to use inorganic anti-corrosion coatings, such as silicate coatings and zinc phosphate coatings. These coatings possess excellent chemical resistance and adhesion, providing reliable protection even in situations where surface treatment is difficult. In summary, for existing LNG storage tanks that require secondary coating, special anti-corrosion coatings with low surface treatment can be used for corrosion protection. However, experiments and tests need to be conducted based on specific conditions to ensure that the selected coating can provide durable and reliable protection for the outer wall of the storage tank. At the same time, regularly checking and maintaining the condition of the coating is also an important measure to ensure its service life. .

This post was last edited by Wang Wei2 on 2023-8-6 at 12:40. Some thoughts on the development and use of low-surface-treatment coatings? Market demand: Not only is low-surface-treatment coating required for the secondary painting of existing LNG tanks, but similar low-surface-treatment coatings are also needed for storage tanks, steel structures, bridges, and so on that undergo secondary painting. The demand in this market can be described as enormous. Materials currently in use: The reason for this is that in China, conventional anti-corrosion coatings are still chosen for secondary coating applications. These materials require a metal surface treatment level of Sa2.5; otherwise, the coating will not be able to meet the designed service life, and failure of the coating usually occurs after 1 to 2 years of use. Status of materials with low surface treatment: There are currently no well-established materials with low surface treatment; neither are there any materials recommended by **standards or industry standards. So, this is a great assignment given to us, the material and corrosion engineers. The advantage of using low-surface-treatment coatings lies in the limitations imposed by conventional materials on-site: currently, in corrosion protection applications, it is the coating that determines the surface treatment of the metal. The coating currently in use is of only one type; it requires thorough treatment of the metal surface, with a standard of Sa2.5 being necessary, although in some cases this standard can be reduced to St3. Requirements for secondary coating equipment, etc.: Due to environmental constraints such as environmental protection, fire prevention, and explosion prevention at the site, the use of conventional materials is restricted. In some locations, construction is not possible; in others, it is necessary to proceed with the work, forcing a compromise on the quality of construction. Features of low surface treatment materials: Low surface treatment materials do not require high levels of treatment for the metal surface; a grade of St2 or lower as per mechanical testing standards is sufficient. It enables the application of a second coat in compliance with environmental, fire, and explosion prevention requirements on site. It can shorten the construction time and reduce construction costs. Significance of developing low-surface-treatment coatings: By using low-surface-treatment coatings, first of all, the level of surface treatment required for metals is reduced ； Second, it overcomes the limitation that most conventional coatings cannot be applied on-site ； Third, it reduces construction costs ； Fourth, and also the main reason, is the huge demand in the anti-corrosion market for coatings with low surface treatment. Current status of low-surface-treatment coatings: At present, there are no standard options available in China for low-surface-treatment materials. We need to continuously conduct material research and development, draw lessons from experience, and keep practicing; once the conditions are right, standards can be developed for use as a reference by the anti-corrosion industry.