Cracks in titanium coiled tubes
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Titanium coil: In a methanol-based system with a pH of around 6, 800 ppm of chloride ions, 9% bromide ions, and 0.2% water content – why does cracking occur? I’d like to discuss this with fellow sailors
The usage time is basically only one or two months
It should be stress corrosion, caused by chloride and bromide ions; a metallographic analysis should be conducted for confirmation……
Based on the components and materials of yours, it seems to be a case of electrochemical corrosion. Electrochemical corrosion: Electrochemical corrosion refers to the corrosion of metals in an electrolyte solution due to electrochemical processes; its essence lies in the redox reactions that occur between the metal and the medium. Both intergranular corrosion and stress corrosion cause material failure through this mechanism. 1. Intergranular corrosion: It occurs preferentially along the grain boundaries, breaking down the bonds between grains and leading to a deterioration in the material’s mechanical properties. 2. Stress corrosion: Under tensile stress, the corrosive environment acts in conjunction with the stress to cause cracking, a phenomenon commonly seen in materials such as stainless steel and aluminum alloys. Both types of corrosion depend on the electrochemical environment and can lead to catastrophic consequences such as pressure vessel leaks and failures in chemical equipment. Solution: It is recommended to use an external circulation heat exchanger instead of a coil heat exchanger, with the heat exchanger material being silicon carbide.
Thank you all; welcome to the experts who will share their opinions
Please let me know how to perform metallography. Thank you
How should I inform about this? Contact a qualified company and send it to them. If a report isn’t required, any engineering university can handle it.
Chloride ion concentration, even at very low levels, can easily lead to SCC in acidic systems.