Titanium tubes are particularly resistant to crevice corrosion, and crevice corrosion occurs only in a few chemical media. The crevice corrosion of titanium is closely related to the temperature, chloride concentration, pH value and the size of the crevice. It is reported that the temperature of wet chlorine gas is easy to produce crevice corrosion when the temperature is above 85℃. Practice has proved: reduce the temperature is to prevent crevice corrosion is one of the effective methods, in the high temperature sodium chloride solution has also occurred in the titanium crevice corrosion. In short, for the parts and components prone to crevice corrosion, such as sealing surfaces, tube plate and tube expansion parts, plate heat exchanger, tower plate and tower contact parts and tower fasteners should be used Ti - 0.2Pd and other titanium alloys should be used in the design of the crevice should be avoided and stagnant flow area. Such as tower fasteners should try not to use bolt connection. Pipe plate and tube with expansion and sealing welding structure is better than simple expansion, for the flange sealing surface, should not be used asbestos gasket, should be used Teflon film wrapped asbestos gasket.
High temperature corrosion
The high temperature corrosion resistance of titanium tube depends on the characteristics of the medium and the performance of its own surface oxide film. Titanium in the air or oxidizing atmosphere, as a structural material can be used up to 426 ℃, but at about 250 ℃, titanium began to absorb hydrogen significantly, in a completely hydrogen atmosphere, when the temperature rises to 316 ℃ or more, titanium absorbs hydrogen to become brittle. Therefore, in the absence of extensive testing, titanium should not be used for temperatures higher than 330 ° C above the chemical equipment, from the absorption of hydrogen and mechanical properties and other considerations, the use of full titanium pressure vessels shall not exceed 250 ° C, heat exchangers with titanium tubes using the upper limit of the temperature of about 316 ° C.
Stress corrosion
In addition to a few kinds of media, industrial pure titanium stress corrosion resistance is good, the phenomenon of stress corrosion caused by titanium equipment damage is still rare. Industrial blunt titanium only in fuming nitric acid, some methanol solution or some hydrochloric acid solution, high temperature hypochlorite, temperature of 300 ~ 450 ℃ molten salt or NaCl atmosphere, carbon disulfide, hexane and dry chlorine gas and other media to produce stress corrosion. The tendency of titanium to rupture by stress corrosion in nitric acid increases gradually with the increase of NO2 content and the decrease of water content. In anhydrous nitric acid containing 20% free NO2, the tendency of titanium stress corrosion reaches large. In concentrated nitric acid containing more than 6.0% NO2 and less than 0.7% H2O, even at room temperature, industrial pure titanium will occur stress corrosion rupture. China in 98% concentrated nitric acid in the use of titanium equipment has occurred serious stress corrosion and explosion. Industrial pure titanium in 10% hydrochloric acid solution, there is stress corrosion rupture sensitivity, containing 0.4% hydrochloric acid plus methanol solution in titanium stress corrosion.
In summary, titanium in acid and alkali corrosion resistance is very strong, it can form an oxide film in acid and alkali, but there are conditions, I hope to help you in the use of our materials.
