As we know, among the plates of plate heat exchanger, titanium plate is unique for its excellent resistance to corrosion. And in the selection of gasket, viton gasket is famous for resistance to acid and alkali and other chemicals. So can they be used together to improve the corrosion resistance of plate heat exchanger?
In fact, Titanium plate and viton gasket cannot be used together. But why? It is the corrosion resistance principle of titanium plate that the two things cannot be used together, because titanium plate is easy to form a layer of dense titanium oxide protective film on the surface, this layer of oxide film can be rapidly formed in the oxygen-containing environment after destruction. And this allows the destruction and repair (repassivation) of the oxide film to be maintained in a stable state, protecting the titanium elements inside form further destruction.
A typical pitting corrosion picture
However, when titanium metal or alloy in the fluorine-containing environment, under the action of hydrogen ions in water, the fluoride ions from the viton gasket react with the metal titanium to produce soluble fluoride, which makes the titanium pitting. The reaction equation is as follows:
Ti2O3+ 6HF = 2TiF3+ 3H2O
TiO2+ 4HF = TiF4+ 2H2O
TiO2+ 2HF = TiOF2+ H2O
Studies have found that in acidic solution, when fluoride ion concentration reaches 30ppm, the oxidation film on titanium surface can be destroyed, indicating that even if a very low concentration of fluoride ion will significantly reduce the corrosion resistance of titanium plates.
When titanium metal without the protection of titanium oxide, in the corrosive environment containing hydrogen of hydrogen evolution, titanium will continue to absorb hydrogen, and REDOX reaction occurs. Then TiH2 is generated on the titanium crystal surface, which accelerates the corrosion of the titanium plate, forming cracks and leading to the leakage of the plate heat exchanger.
Therefore, in plate heat exchanger, titanium plate and viton gasket must not be used together, otherwise it will lead to corrosion and failure of plate heat exchanger.
Shanghai Heat Transfer Equipment Co.,Ltd.(SHPHE) has rich service experience in plate heat exchanger industry, and also has related physical and chemical laboratories, which can quickly and accurately determine the material of plate and gasket for customers in the early stage of selection, to ensure the safe and reliable operation of equipment.
Post time: Feb-17-2022