Research And Production Of Dual Layer Fbe Powder Coatings For Long Distance Pipeline

Aiming to the solving the failure of Cathodic Protection (CP) in major 3PE anti-corrosion system of domestic long-distance oil/gas pipeline and improving the performance of gouge-resistant during assembling and burying pipeline, we start the R&D with Dual Layer FBE (Fusion Bonded Epoxy) protection system for better anti-corrosion performance.As the total DFT of Dual Layer is about 1000μm, the powder coatings may accrue sagging, porosity, interface adhesion, bending and flexibility. We start with DICY curing agent and Phenol curing agent to set up formulation model. Phenol system presents better molten flow length during coating thickness reach 400-1000 um, which effectively prevent from sagging problem. So the formulation model of primer and top coat is based on Phenol curing system.During pipe coating, the film thickness range of primer and top coat is in 400-600 um, it's not easily to drive air mixed in spraying powder out from melting powder, and porosity therefore accrues. To reduce porosity is also one of our R&D target, as porosity definitely affect CD (Cathodic Disbondment) performance. Finally we find way to ensure porosity less than class 4 during powder application by adjusting the ratio of curing agent and appropriate epoxy resin. Another factor can also affect porosity, that's the extrusion dispersion level of mixed raw when producing powder coatings. We therefore set up different temperature parameters at 4 temperature control areas by adjusting cooling and electricity heating.Due to primer is first protective layer to touch pipe substrate, the primer CD at 65℃,28days is most important; Top coat need to subject to outside mechanical impact when pipe assembling and burying, the performance of abrasion-resistance and gouge-resistance is important issue. We select crystal SiO2 as filler, appropriate epoxy and related catalyst as main functional material to comprehensively control the reactivity and gel time, to enhance CD, bending performance .Finally, that the reaction peak temperature of top coat is 17℃lower than primer ensures the topcoat can react with uncured primer to combine together and build an excellent adhesion between primer and topcoat. That Tg1 (powder glass transition temperature ) is 5℃higher than local Dual Layer powder means the powder's storage ability is much better; That Tg2 (cured film glass transition temperature ) is 5℃higher than local Dual Layer powder means the powder can be selected for special pipeline with higher operation temperature. In general, this Dual Layer can meet the industrial requirement of Cathodic Disbondment test, bending, Tg2 and Delta H, even higher than domestic standard, and passed the examination twice implemented by CNPC LangFang institute. That means this Dual Layer protection system is in line with domestic market specification: Q/CNPC 38-2002 and West-East specification CQE200700506, and the latter is very close to CAN/CSA Z 245.20.