As part of EUROPIPE’s hydrogen research program, the company recently tested different flow coatings in pure hydrogen to evaluate their suitability for use in hydrogen transport. Suitability tests conducted by the Salzgitter Mannesmann Research Company (SZMF) have confirmed that EUROPIPE's pipes internally coated with epoxy-based flow coatings are capable to be used for hydrogen pipelines in a 100 bar pure hydrogen atmosphere.

The investigated test specimens originate from pipes internally lined at MÜLHEIM PIPECOATINGS (MPC) with epoxy-based flow coat materials TEKNOPOX 3296-06 (82 Vol.- % solid content) and TEKNOPOX 3297-00 (97 Vol.-% solid content) supplied by TEKNOS. The flow coating thickness of all specimens was between 61 µm and 120 µm.

According to EUROPIPE, the testing protocol followed API RP 5L2 for the resistance to gas blistering and EN 10301/ISO 15741 for the resistance to gas pressure variations (cyclic testing) and hydraulic-pressure blistering. These standards are commonly used for qualification testing of internal coatings for non-corrosive gases. The “blistering tests” are usually performed with nitrogen as pressurizing gas to simulate the effect of spontaneous pressure drops on the internal coating. For the performed tests, hydrogen was utilized as a pressurizing gas to investigate how or whether hydrogen, having the smallest molecular diameter, would influence the resistance of the coating to spontaneous pressure drops. Missing resistance can lead to blistering, delamination or reduced adhesion of the internal coating.

The specimens were placed in an autoclave and pressurized with hydrogen to 100 bar.
For the testing according to API RP 5L2, the pressure was released after 24 hours in less than 5 seconds, to simulate a very rapid pressure drop.

In comparison with the API RP 5L2, the testing method according to EN 10301/ISO 15741 exhibited 10 cycles of pressure variations. Moreover, the behavior of the flow coatings when subjected to pressure variations in a liquid environment (water saturated with CaCO3) was investigated.

After all tests, EUROPIPE said the surface of the specimens were examined and the adhesion of the flow coating was determined according to ISO 2409 (cross-cut test). Formation of blisters was not observed and the delamination parameter were determined as “0” for all specimens confirming an excellent adhesion of the internal coating after the performed tests, ensuring that the company's pipes, with internal coating applied by MPC, are suitable for future hydrogen pipelines.