The effect of 2-methylimidazole as applicator for the low temperature of fusion bonded epoxy in pipeline system

Epoxy-based coatings such as Fusion Bonded Epoxy (FBE) are widely used for gas/oil pipelines because they exhibit high chemical resistance, very low permeability to chloride ions, good mechanical flexibility, and strong adhesion to steel. On the pile pipe (>40 inches in diameter), it is challenging to apply the coating due to the ability induction machine to heat the pipe according to the application temperature recommended by the paint manufacturer. In this work, adding 1, 2, 3 % wt 2-methylimidazole (2-MI) was carried out into the epoxy phenol-formaldehyde base mixture, glycidyl ether polymer to accelerate the curing process and lower the application temperature. Thermal analysis was conducted using Differential Scanning Electron (DSC), where the addition of 3% wt 2MI resulted in a maximum decrease to 134.76°C due to activation energy reduction. The addition of 2-MI acts as a catalyst in the curing reaction, as shown in the Fourier Transform Infrared (FTIR) test results, where 2-MI opens the epoxy ring to increase the curing process. Electrochemical characterization analysis using potentiodynamic polarization shows the maximum corrosion rate is 0.00991 mm/year, and the current density is 0.847μA/cm2, upon addition of 1% wt 2-MI. Electrochemical Impedance Spectroscopy (EIS) determines the charge transfer resistance and maximum coating capacitor capacitance at the addition of 1%wt 2-MI of 9.9 kω and 8.45 x 10-5 F. Cathodic Disbondment Test (CD-Test) results show the disbondment radius of the coating under the influence of the cathodic protection current is 4.32 mm. Moreover, adding a higher concentration of 2-MI reduces the crosslinking density owing to the presence of epoxy-imidazole adducts. The addition of 2-MI did not have a significant effect on the porosity of the coating with low-temperature applications of 170-175oC where all samples reached rate 1 in longitudinal cross-section and the interface between the coating and the steel pipe surface. On top of that, adding 1% wt 2-MI is suitable for low-temperature applications at 170-175°C in piles with excellent coating performance.