Commonly used corrosion-resistant materials

Thread Content

1. TA2 pure titanium is a silver-white metal with many excellent properties. Titanium has a density of 4.54 g/cm³, which is 43% lower than that of steel. It is slightly heavier than magnesium, the well-known light metal. Its mechanical strength is roughly comparable to that of steel; it is twice as strong as aluminum and five times as strong as magnesium. Titanium is heat-resistant, with a melting point of 1668°C. Pure titanium has excellent resistance to oxidation and corrosion by corrosive media. At room temperature, a very thin and dense oxide protective film readily forms on the surface of titanium. This film can resist the effects of strong acids and even aqua regia, exhibiting excellent corrosion resistance. Therefore, while ordinary metals become riddled with holes in solutions of acids, bases, and salts, titanium remains unharmed. The recommended operating temperature for titanium materials is below 250°C. In oxidative media, the temperature may be raised appropriately, but should not exceed 420°C. Titanium and its alloys can undergo spontaneous explosion in dry chlorine gas, pure oxygen (PO2 > 35%), and fuming red sulfuric acid; they also corrode very rapidly in hydrofluoric acid. Therefore, they cannot be used in these environments. 2. In addition to possessing the characteristics of pure titanium, TA9 benefits from the addition of a small amount of the precious metal palladium (0.2% Pd) to commercially pure titanium. The palladium dissolves into the medium, forming palladium ions, which reduce the hydrogen overpotential of the alloy in the medium. This causes a significant positive shift in the stable potential of the titanium alloy, thereby enhancing its corrosion resistance in oxidative media. Particularly in high-temperature chloride solutions, TA9 exhibits the best resistance to crevice corrosion among all titanium alloys. The main characteristics of TA9 are: 1. Its corrosion resistance in reducing media is significantly improved compared to pure titanium; it exhibits good corrosion resistance in hydrochloric acid, dilute sulfuric acid, as well as hot formic acid and citric acid. 2. In an oxidizing environment, it exhibits excellent corrosion resistance comparable to that of pure titanium; it can be used in environments where reduction and oxidation alternate. 3. The hydrogen absorption resistance is better than that of pure titanium. 4. It exhibits excellent resistance to crevice corrosion in high-temperature and high-concentration chloride environments; it does not corrode in seawater at 250°C. 5. It has good workability and formability; it can be used to produce various metallurgical semi-finished products and manufacture a variety of industrial equipment. 6. Contains the precious metal palladium, which increases costs and limits its widespread application. The Ti-0.2Pd alloy has found extensive applications in industries such as metallurgy, chemical engineering, and petroleum. Mainly used for heat exchangers and nozzles in environments containing dilute hydrochloric acid, sulfuric acid, and prone to crevice corrosion. Equipment and components such as flange sealing rings and diamond-shaped gaskets. 3. TA10 exhibits good resistance to crevice corrosion in high-temperature, low-pH chloride solutions and weakly reducing acids. This alloy exhibits better overall corrosion resistance than commercially pure titanium in sulfuric and hydrochloric acids, but inferior to titanium-palladium alloys; however, in aqua regia and nitric acid, it performs better than palladium alloys. 4. TC4 is the most widely used titanium alloy. In addition to excellent corrosion resistance, it also has good overall mechanical properties, good weldability, and can be heat-treated for strengthening. It can maintain good ductility and toughness at low temperatures ranging from -196 to -253°C. 5. TB7 is currently the titanium alloy with the best corrosion resistance in reductive media; it is particularly suitable for use in strongly reductive media such as high-temperature hydrochloric acid and sulfuric acid. 6. 310SS, 304/304L, and 316/316L are particularly suitable for use in oxidizing media such as nitric acid ； Weaker organic acid solutions ； Various inorganic acids, organic acids, bases, and salts are acceptable. 7. For 904/904L, various concentrations of sulfuric acid at temperatures below 70°C; it is particularly resistant to intergranular corrosion. 8. The 321SS is particularly suitable for use in oxidative media, such as nitric acid ； Weaker organic acid solutions exhibit stable corrosion resistance in alkaline solutions ； Its corrosion resistance remains stable in reducing media such as hydrochloric acid and sulfurous acid ； It has good resistance to sensitization-induced intergranular corrosion. 9. In chlorine-containing environments, SAF2205 exhibits better pitting resistance than 18-5Mo type duplex stainless steels. Its resistance to crevice corrosion is comparable to that of 316L. It also demonstrates excellent resistance to chloride stress corrosion. In most media, its resistance to uniform corrosion is superior to that of 304L and 316L. 10. SAF2507 is mainly used in harsh media, especially in chlorine-containing environments such as seawater. It exhibits excellent resistance to stress corrosion cracking, pitting, and crevice corrosion. The critical pitting temperature and critical crevice corrosion temperature are significantly higher than those of SAF 2205 and 904L austenitic stainless steels. It shows no tendency toward intergranular corrosion; however, its resistance to chloride-induced embrittlement in H2S-Cl- environments is inferior to that of high-chromium-nickel austenitic stainless steels. 11. CD-4MCu is resistant to corrosion by dilute sulfuric acid and phosphoric acid. Wear-resistant. 12. 1Cr13 exhibits good corrosion resistance in weakly corrosive media at temperatures not exceeding 30°C (such as hydrochloric acid solutions, dilute nitric acid, certain organic acids at low concentrations, and food-related media) ； It also has sufficient rust and corrosion resistance under conditions of fresh water, steam, and humid atmosphere ； It has sufficiently high thermal stability below 700°C. 13. Due to its slightly higher carbon content compared to 1Cr13, 2Cr13 has somewhat lower toughness and corrosion resistance ； Its corrosion resistance is the same as that of 1Cr13. It is mainly used for manufacturing blades, hot oil pumps, bushings, impellers, valve stems, and hydraulic press valve plates, etc. 14. 3Cr13 has higher strength, hardness, and hardenability than 1Cr13 and 2Cr13. Its corrosion resistance and thermal stability below 700°C are lower than those of 1Cr13 and 2Cr13. It is mainly used for manufacturing structural components requiring high strength, as well as wear-resistant parts subjected to high mechanical stresses and certain concentrations of corrosive media, such as pump shafts and cutting tools operating at temperatures below 300°C. 15. In many media, even in highly corrosive ones, Ni often exhibits excellent corrosion resistance. It has good resistance to caustic alkalis or their molten states; no hydrogen is released during the corrosion process. Corrosion of Ni only occurs when certain oxidizing ions are present in the medium. N6 can also form a passive film in oxidative media, thus exhibiting good corrosion resistance to such media. 16. Hastelloy B: Phosphoric acid at various concentrations where the temperature is below 65°C and the concentration is below 85%, as well as phosphoric acid at high temperatures and high concentrations; non-oxidizing neutral and alkaline solutions. 17. Hastelloy C exhibits good corrosion resistance in acetic acid without air charging and in the absence of oxidizers. It exhibits good corrosion resistance in wet chlorine, oxidative and non-oxidative chloride solutions, sulfuric acid containing oxidative salts, sulfurous acid, phosphoric acid, formic acid, hydrogen fluoride at high temperatures, nitric acid at room temperature at full concentration and at lower concentrations at higher temperatures, and sulfurous acid at any concentration and temperature. 18. Monel alloy exhibits good corrosion resistance in high-temperature hydrogen fluoride gas and hydrofluoric acid solutions, as well as in molten caustic alkalis, medium- and alkaline salts, and their solutions. It is mainly used for products such as heat exchanger equipment, boiler feedwater heaters, and pumps and valves in the chemical, petrochemical, and offshore development industries. Alloys No. 19 and 20 are mainly used in high-temperature dilute sulfuric acid, a corrosive medium with a temperature of ≤130°C and a concentration of around 40%.