What Does Hydrogen Blistering Mean?
Hydrogen blistering is the blistering of metal surface due to the presence of hydrogen. Blistering is an irreversible process and usually occurs in metals with low strength, i.e. less than 80 ksi yield strength, and causes permanent reduction in the mechanical strength of the metal.
With the help of trenchless rehabilitation techniques for inspecting pipelines, such damages can be detected before failure of the pipe occurs.
Trenchlesspedia Explains Hydrogen Blistering
Hydrogen blistering occurs when hydrogen ions reduce to hydrogen atoms and adsorb on the metal surface. Where there are voids around inclusion, these hydrogen atoms diffuse through the metal and accumulate in these traps. When these hydrogen atoms combine in such a void or trap, they form into hydrogen gas, which accumulates and builds up internal pressure in the void, sometimes becoming high enough to cause the metal to blister.
Hydrogen blistering takes place in metals with low strength, metals exposed to corrosive environments, and during repairs in these metals subjected to high temperatures. Hydrogen blistering can be avoided by:
- Using materials that are resistant to corrosion
- Preventing impurities from entering the metal at the manufacturing stage
- Using coatings that will prevent the penetration of hydrogen
- Reducing the need for welded joints
- Heat treating welds (when weldments are used) to diffuse hydrogen from the metal