Coating is one of main methods to protect pipe line from corrosion. It defenses pipes from moisture, dirty, acid and any kind of chemical action. It gives longer life time of pipe line. However, some failures could jeopardize project and make people get injured due to explosion or any other unexpected events. There is several reasons of failures such as air permeation, water permeation, loss of adhesion, loss of cohesion, blistering, and disbondment etc.
To remove those failures, we apply heat to pipes and water or moisture dries. Also coating material itself is very hot. Increasing temperature both pipes and coating materials can increase the attachment. And coating material is applied bonds. During production, pipes are turning and coating materials are rolling and attached to it with high tensile to direction of outside of pipe. This move is to prevent air contain between pipe and coating.
Even those actions are basic procedure for manufacturers, one thing we must be careful is height of bead. If bead height is too much high, then it makes space between coating and pipe line. Right after coating, it seems coating is perfect and well attached. However, couple of months or years passed, the section would have blister by air. Starting the section, air infiltrates into coating attachment. Finally large section could have more blisters.
The Original Posted by Jethro