**Thermal spray corrosion-resistant coatings can be categorized into the following types based on material composition and application requirements, making them suitable for various corrosive environments:**

1. **Metal-Based Coating**

- **Zinc Coating**: Utilizing a sacrificial anode to protect the substrate, it forms a protective film of basic zinc carbonate in neutral aqueous solutions, offering excellent corrosion resistance. Commonly used for components such as bridges, TV towers, and underground pipelines, this coating, however, exhibits relatively low acid resistance and is best suited for environments with pH levels ranging from 6 to 12.

- **Aluminum Coating**: Offers superior corrosion resistance compared to zinc, particularly excelling in industrial atmospheres containing SO₂ or marine environments. It is suitable for soil pipelines, port components, and marine structures, though its cathodic protection effectiveness is weaker than that of zinc.

- **Zinc-Aluminum Alloy Coating**: Combining zinc’s cathodic protection with aluminum’s corrosion resistance, this coating offers superior overall performance. In the same corrosive environment, its thickness can be reduced, and it exhibits rapid self-healing properties, making it ideal for marine steel structures, oil drilling equipment, and other applications.

- **Nickel-chromium alloys (such as NiCr)**: Resistant to high-temperature oxidation and sulfide corrosion, operating at temperatures exceeding 900°C, making them suitable for high-temperature applications like gas turbine blades and boiler pipes.

- **Stainless steel coating (such as 316L)**: Resistant to acid and alkali corrosion, with low porosity and excellent resistance against erosion by molten metals (zinc, aluminum liquid), making it ideal for repairing chemical equipment.

2. **Ceramic Coating**

- **Aluminum oxide (Al₂O₃)**: Resistant to acid and alkali corrosion, with high chemical stability, it is commonly used in chemical equipment such as pumps, valves, and reactors. Adding a small amount of titanium oxide can enhance its toughness and impact resistance, while also providing excellent wear resistance.

- **Zirconia-based coating (yttria-doped)**: Resistant to high-temperature oxidation and thermal corrosion, with salt-spray resistance exceeding 480 hours and a 50% reduction in the thickness of the TGO layer. Ideal for hot-end components of aeroengines and in marine environments subject to high-temperature corrosion.

- **Chromium Oxide (Cr₂O₃)**: Exhibits outstanding chemical inertness, being virtually insoluble in water, acids, bases, and organic solvents. At high temperatures, it forms a dense passivation layer that effectively shields against corrosive gases such as H₂S and SO₂. After being sealed with epoxy resin, its salt-spray resistance is significantly enhanced—showing no corrosion after 160 hours of neutral salt-spray testing—making it ideal for demanding environments like the battery housings of new-energy vehicles.

3. **Composite Coating**

- **Cr₂O₃-TiO₂ System**: By incorporating TiO₂, the system enhances stability in acidic environments. The composite exhibits superior hydrochloric acid resistance compared to pure chromium oxide, and it also possesses self-healing capabilities—allowing the protective oxide layer to rapidly regenerate upon damage. The bonding strength reaches 67 MPa, while its high-temperature infrared emissivity is improved, making it well-suited for extreme corrosive conditions.

- **Nickel/Chromium Coating**: As a prime example of a heat-resistant and corrosion-proof coating, it combines excellent resistance to high-temperature oxidation with superior durability against chemical media corrosion, making it ideal for use in high-temperature, sulfur-containing gas environments such as gas turbine blades and boiler pipes.

4. **Other Special Coatings**

- **WC-Co Coating**: Wear-resistant and corrosion-proof, with a wide operating temperature range (-180°C to 260°C), making it suitable for marine environment components, as well as chemical fluidized beds, food machinery, and more.

- **Teflon Coating**: Resistant to strong acid/alkali environments, capable of withstanding 98% concentrated sulfuric acid; its low surface energy makes it ideal for chemical corrosion protection applications.