Epoxy Coil Coating Primer (Formulation #2.2) is a formulation that utilizes SHIELDEX® C 303, a high performance non toxic heavy metal free, anti-corrosive pigment specially designed to replace Strontium Chromate in coil coating primers. Epikote 1007 and Epikote 1009 are standard epoxy resins used in coil coating primer applications. UFR 80 is a typical urea based crosslinker used in these applications. The cure response within this formulation was controlled by the use of Epoxy blocked Phosphoric acid (co-catalyst) and Halox 650 (dicarboxylic-acid co-catalyst). These components prevent the interaction of SHIELDEX® anti-corrosive pigment with the acid catalysts and any acid funtionality on the resin systems, thus ensuring maximum cure response.
The SHIELDEX® C 303 anti-corrosive pigment containing epoxy coil primer was applied on Bonder 1303 (ex Chemetall) and Granodine C 108 (ex Henkel) treated galvanised steel test panels. The primer was applied by bar coater to a dry film thickness of 5 – 7 microns. Cure was to a peak metal temperature (PMT) of 216 – 224 °C. A polyester-melamine topcoat was applied to a bar coated dry film thickness of 20 – 25 microns and cured to a PMT of 232 – 241 °C.
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