**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 in marine environments. It is suitable for use in soil pipelines, port components, and marine structures, though its cathodic protection performance 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-sealing 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 (e.g., 316L)**: Resistant to acid and alkali corrosion, with low porosity and excellent resistance against erosion by molten metals (such as zinc and aluminum), 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 (Doped with Yttria)**: Offers resistance to high-temperature oxidation and thermal corrosion, with salt-spray resistance exceeding 480 hours. The TGO layer is thinned by 50%, making it ideal for hot-end components of aero-engines as well as in marine environments subject to high-temperature corrosion.

- **Chromium Oxide (Cr₂O₃)**: Notably chemically inert, it is 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- and corrosion-resistant coating, it combines excellent resistance to high-temperature oxidation with superior durability against chemical media corrosion. It is ideally suited for use in high-temperature, sulfur-containing gas environments, such as 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 and food machinery.

- **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.