Brass preparation for painting

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Le Corbusier
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Re: Brass preparation for painting

Postby Le Corbusier » Sun May 17, 2020 7:38 am

presumably if the edges have been either grit blasted or fibre brushed they too will have the microscopic roughness for adhesion. We always spec. etch priming when using galvanised steel.
Tim Lee

Daddyman
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Re: Brass preparation for painting

Postby Daddyman » Sun May 17, 2020 8:06 am

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

That would be my understanding.

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Paul Willis
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Re: Brass preparation for painting

Postby Paul Willis » Sun May 17, 2020 9:38 am

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;


And to illustrate that point, these are a couple of my E22 having just been primed, and before going under the dust cover to harden off. The colours of the base metals underneath are clearly visible. This is with Comet self-etch primer, IIRC:

E22 primer 1.JPG


E22 primer 2.JPG


The nickel silver coupling rods are being primed as they are painted vermilion on the prototype.

Cheers
Flymo
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Edward45
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Re: Brass preparation for painting

Postby Edward45 » Mon May 18, 2020 7:19 am

Has anyone ever used or had any experience of "Quickshine Brass & Copper Bath" ?

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Paul Townsend
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Re: Brass preparation for painting

Postby Paul Townsend » Mon May 18, 2020 8:03 am

I have just added some notes re using air grit blasting on Alan's thread
viewtopic.php?f=39&t=3837&p=75494#p75494


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