Differential scanning calorimetry and optical photo microscopy examination for the analysis of failure of fusion bonded powder epoxy internal coating

• Research paper based on a case study which is a serious issue in the oil field.
• Multitechnique approach based on field study as well as laboratory investigation was used to understand the failure of epoxy coating.

An investigation was conducted to find out the reason behind the failure of the powder epoxy internal coating from production flow line of Large Scale Pilot Project (LSP) from an oil exploration in Kuwait. The internal coating was completely detached and peeled out in the form of curling from the substrate, and causing the production flow line to be plugged with the deposit of paint debris. The production operation of oil supply from the LSP well was stopped due to this failure and the pipeline was replaced. Multiple field techniques and laboratory approaches were used to find out the reason behind the coating failure. The research work involved utilizing the analysis of the surface carbon steel substrate with new epoxy coated sample as compared to the failed one using differential scanning calorimetry (DSC) and optical and photomicroscope examination. The overall results indicated that the failure was due to the combined effects of the improperly cured coating as determined by differences in the glass transition temperature (Tg), and differential thermal expansion properties between the steel tube and coating causing shrinkage stresses resulting in disbonded coating. This was enhanced by the expansion of corrosion oxide products as a sequence of ineffective substrate pre-treatment.