Mordent T wash first then acid etch primer before black of your choice
So that doesn't affect the galvi coating? I'll google it.
The t wash ages the galvanise a bit so the paint will stick otherwise it throws it off
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Excellent many thanks
miktdish
Guns n Chainsaws
I really don't think @Def90man would give you 'made up/spurious' advice.
Let me expand ... you can't paint directly on galvanised metal, you need to remove the hydroxides and carbonates that a galvanised surface produces to protect itself (it's the equivalent of 'rust' on steel).
Phosphoric Acid removes it, a combination of water and oxygen (ie air) will regenerate it. Mordant T wash contains a copper dye so you can see where you have painted/lathered it on and where the reaction has taken place. It only lasts for a few hours so you need to paint it (stopping the water/oxgen from reacting with the zinc) as soon as possible.
Primers are porous so you need to seal it with a topcoat as soon as the primer is dry.
You can get galv-in-one topcoats if you can't be arsed to prime/undercoat first.
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dag019
Well-Known Member
^^ This
There are lots of different etch primers but I have found them all to perform basically the same. I have had good results with hammerite special metal primer which you can buy from homebase/B&Q/etc rather than needing a paint specialist.
dag019
Well-Known Member
That is different to my understanding of how t-wash worked, although my understanding is very un-scientific because I have never looked up the actual science.I really don't think @Turboman would give you 'made up/spurious' advice.
Let me expand ... you can't paint directly on galvanised metal, you need to remove the hydroxides and carbonates that a galvanised surface produces to protect itself (it's the equivalent of 'rust' on steel).
Phosphoric Acid removes it, a combination of water and oxygen (ie air) will regenerate it. Mordant T wash contains a copper dye so you can see where you have painted/lathered it on and where the reaction has taken place. It only lasts for a few hours so you need to paint it (stopping the water/oxgen from reacting with the zinc) as soon as possible.
Primers are porous so you need to seal it with a topcoat as soon as the primer is dry.
You can get galv-in-one topcoats if you can't be arsed to prime/undercoat first.
Rust Converter, Chassis Paint, Rustproofing, Sound Deadening
Everything you need to restore your project, make it, sell it, use it. Thats why we provide the best advice in the UK!www.buzzweld.co.uk
My understanding is t-wash is just copper suplphate solution and just replicated the aging process of galv. If you leave galv outside for a few years you can pint it no problem without an etch primer, it is only new shiny galv that paint will not stick to. As it ages it dulls as the surface layer oxidises similar to rust (as states above). I also was under the impression beacsue of this that once painted with t wash there was no time limit to prime as it will not go back to the new and shiny it was before, it is a chemical treatment not something that wear s off.
Turboman
Mab An Gov
Guessing this is an edit, as I got tagged.
I didn't give any advice, but would agree with what he said.
Although in fact, I don't paint galv, it will last a good 25-30 years anyway, and as I am now 60, what happens after that is unlikely to be of any concern to me.
miktdish
Guns n Chainsaws
Yes ... sorry, my mistake.
