Corrosion resistance of other metals and alloys in sulfuric acid

Gold and platinum have excellent corrosion resistance in sulfuric acid. Because of their rarity and high cost, they can not be used as engineering alloys in industry. Only in some special occasions, such as the few artificial silk nozzles requiring minimal corrosion and absorption tower of reagent pure sulfuric acid which cannot be polluted can be used in a small amount.
Tantalum is very corrosion resistant except for the very strong and hot sulfuric acid. Zirconium is very corrosion-resistant in sulfuric acid under 60% concentration and boiling sulfuric acid, and also in concentrated sulfuric acid below 92 ℃. Zirconium hafnium alloy also has good corrosion resistance in sulfuric acid.
Titanium is not corrosion resistant in sulfuric acid except for its very thin concentration, but titanium is sometimes used as corrosion inhibitor, for example, in equipment for smelting nickel ore, titanium is used in tons. The addition of some alloy elements in titanium can improve its sulfuric acid resistance. The Ti 68mo32 has good corrosion resistance in sulfuric acid.
Molybdenum has excellent corrosion resistance in sulfuric acid. The corrosion rate of molybdenum in sulfuric acid under 10-95% 70 ℃ is less than 0.025mm / year, and that in sulfuric acid below 50% to boiling is less than 0.125 mm / year, in 204 ℃, 10% sulfuric acid is less than 0.025mm / year, in 204 ℃, 20% sulfuric acid, less than 0.1mm / year.

Alloy C-22 is a versatile nickel-chromium-molybdenum-tungsten alloy with improved resistance to both uniform and localized corrosion as well as to a variety of mixed industrial chemicals. It has excellent resistance to oxidizing aqueous media including wet chlorine and mixtures containing nitric acid or oxidizing acids with chloride ions.

Alloy C-22 has exceptional resistance to a wide variety of chemical process environments, including strong oxidizers such as ferric and cupric chlorides, chlorine, hot contaminated solutions (organic and inorganic), formic and acetic acids, acetic anhydride and seawater and brine solutions.

Alloy C-276 (UNS N10276) is a nickel-molybdenum-chromium wrought alloy that is generally considered the most versatile corrosion-resistant alloy available. Alloy C-276 is an improved wrought version of alloy C in that it usually doesn't need to be solution heat-treated after welding and has vastly improved fabricability. This alloy resists the formation of grain-boundary precipitates in the weld heat-affected zones, thus making it suitable for most chemical process applications in the as-welded condition.

Alloy C-276 has outstanding resistance to localized corrosion and to both oxidizing and reducing media. Because of its versatility, alloy C-276 can be used where upset condtions are likely to occur or in multipurpose plants.

Alloy C-276 has exceptional resistance to a wide variety of chemical process environments, including strong oxidizers such as ferric and cupric chlorides, hot contaminated media (organic and inorganic), chlorine, formic and acetic acids, acetic anhydride and seawater and brine solutions. It is used in flue gas desulphurization systems because of its excellent resistance to sulphur compounds and chloride ions encountered in most scrubbers. Alloy C-276 has excellent resistance to pitting, stress-corrosion cracking and to oxidizing atmospheres up to 1038°C (1900°F). It is also one of the few materials that withstands the corrosive effects of wet chlorine gas, hypochlorite and chlorine dioxide.