Scalefour Forum

Le Corbusier wrote:presumably if the edges have been either grit blasted or fibre brushed they too will have the microscopic roughness for adhesion.

Daddyman wrote: He then says the "real" primer is etching primer, "which has an important job to do on non-ferrous metals. After application, an acid in the mix, over a period of 12-24 hours, eats into the metal surface, creating the microscopic roughness that the paint requires to improve adhesion." (This acid, he says later, is our old friend phosphoric acid!) Two top tips for etching primer (as opposed to car primer) are (1) this thing about leaving it for 24 hours (for the Precision two-part primer) (don't touch it at all during this time - who knows what the blend of finger-print grease and, these days, alcohol-rich hand sanitiser, will do to mess up the process); and (2) it can (should?) be thin enough that it doesn't obscure the different colours (brass, whitemetal, resin, solder) beneath;