Corrosion repair methods for natural gas pipelines

To further illustrate the technical superiority of protective coatings, the most widely used anti-corrosion technologies and the most representative types of coatings are listed and compared as follows: Table 1. Performance comparison of protective coatings and common anti-corrosion products. Product name, Adhesion, Corrosion resistance, Weather resistance, Wear resistance, Aesthetic appeal, Energy consumption and pollution, Overall evaluation: Hot-dip galvanizing – Extremely high; extremely poor resistance to acids, alkalis, and salts; turns black within half a year in air; high wear resistance; monotonous colors with short-lasting aesthetic effect; high pollution and energy consumption; environmentally problematic and gradually being phased out. Fluorocarbon paint – Poor adhesion; extremely high corrosion resistance; strong weather resistance with a long service life; relatively good wear resistance; monotonous colors with poor aesthetic appeal; high corrosion resistance but with noticeable defects. Dacromet – Extremely high adhesion, but not suitable for zinc, copper, or magnesium alloy substrates; excellent salt resistance but average acid resistance; changes color within a year in areas with severe acid rain and rusts the following year; poor hardness and wear resistance; monotonous colors with poor aesthetic appeal; requires curing at 300°C; contains 6+ chromium, posing potential pollution risks; poor acid resistance and aesthetic appeal, resulting in limited applications. Epoxy paint – Relatively good adhesion; fairly good performance; extremely poor resistance; fades after 2 hours of exposure to sunlight and becomes powdery after 8 months; poor hardness and wear resistance; average performance, leading to limited applications. Polyurethane paint – Relatively good adhesion; fairly good performance; extremely poor resistance; fades after 2 hours of exposure to sunlight and becomes powdery after 8 months; poor hardness and wear resistance; average performance, leading to limited applications. Protective coatings – Extremely high adhesion, suitable for various metals and non-metals; full resistance to acids, alkalis, and salts, with outstanding corrosion resistance; strong performance with a service life of over 20 years; hardness can reach up to 6H, providing excellent wear resistance; rich and vibrant colors with great aesthetic appeal; can dry naturally or be cured at 80–200°C; contains 3+ chromium, causing no pollution; can be used for both anti-corrosion purposes and decoration; has broad application prospects in both military and civilian fields. It is clear from this comparison that protective coatings are advanced coatings with excellent overall performance. They possess the advantages of fluorocarbon paint and Dacromet in terms of anti-corrosion capabilities, while avoiding their weaknesses. They hold great market potential, especially in specialized anti-corrosion applications. 　　　II. Application Areas of Protective Coatings Generally speaking, magnesium alloy protective coatings can be used for the anti-corrosion treatment and aesthetic decoration of all metal or non-metal surfaces. Based on the technical advantages of magnesium alloy protective coatings, breakthroughs can be achieved primarily in the following areas: 1. As special coatings for heavy-duty industrial corrosion protection, they are widely used in the flue gas desulfurization processes of industries such as chemicals, thermal power generation, steel manufacturing, non-ferrous metals, oil refining, and natural gas, for the heavy-duty corrosion protection coating of desulfurization devices or facilities. 　　　2. As a high-performance marine anti-corrosion coating, it is widely used for the anti-corrosion and decorative purposes of ships, containers, port equipment and facilities, oil drilling platforms, oil and gas pipelines, offshore bridges, navigation markers, lighthouses, etc. 　　　3. Used for the corrosion protection and decoration of metal surfaces that are directly exposed to the atmosphere, acid rain, and humid environments. Anti-corrosion and decorative treatment for items such as power and communication towers, construction scaffolds and crane towers, bridges, steel cables and anchors of cable-stayed bridges, tunnels, railway and light rail tracks along with their metal facilities and components, oil and gas storage tanks, oil and gas pipelines, highway crash barriers, road signs, and so on. 　　　4. Used for corrosion protection and decoration on vehicle surfaces. Surface corrosion protection or decoration for aircraft, automobiles, locomotives, vehicles, all types of bicycles (including those made of aluminum alloy and magnesium alloy), various types of ships, marine equipment, quay machinery, and port facilities ； Corrosion protection and coating of military firearms and equipment, such as tanks, armored vehicles, heavy artillery, and floating bridges. 　　　5. Used for surface anti-corrosion and decoration of metal and non-metal furniture, electrical appliances, ironware, wooden products, tools, and agricultural tools. 　　　6. Applied in water conservancy and hydropower facilities, such as steel gates that are submerged underwater for long periods or exposed to humid environments, the lifting equipment for these gates, as well as for the anti-corrosion treatment and aesthetic decoration of pipelines. 　　　7. Used as a highly weather-resistant coating for the anti-corrosion protection of building surfaces and their associated facilities. It is particularly suitable for the anti-corrosion treatment and decorative finishing of large and medium-sized steel structure buildings (such as the steel structure of the Beijing National Stadium). It can also be used for painting exterior and interior walls of residential buildings, as well as for the anti-corrosion and decorative purposes of outdoor railings in homes, thereby extending the service life of buildings and metal structures. With just one application, it requires no maintenance for many years, and so on.