Painting Galvanised Sheeting

Bluscreendream

Hi guys,

Looking for some advice on painting galvanised corrugated roof sheeting. The challenge of course is the zinc content on the galv and most paints will not adhese correctly and will eventually peel. I've done some reading up on etch primers and that but as I have 19 12 foot sheets to paint :rolleyes: financially this is simply not feasible for me.

I read on one forum that using an electric sander with the correct gauge pad would 'roughen up' the surface a bit which would then create a grip to for example apply a standard oxide paint. Could anyone advise if this true or advisable?

Many thanks, B

jonon9

OK may sound silly but how about bringing back where you got it from and add the extra cash and buy the already coated sheets colour depending of course. surely it would be cheaper than painting 19 sheets by hand.

CJhaughey

If you sand the coating you will remove the zinc and start the process of corrosion.
It's nearly impossible to sand corrugated sheeting anyway, you will just rub the top off the peaks and leave the valleys untouched.
Etch prime is the only way to paint the roof and the paint to stay on the roof.

M.T.D

Sorry if this is stating the obvious. The iron is coated with a thin layer of zinc to protect the iron from corrosion. The zinc does this by oxidising first, i.e. it is a sacrificial coating. If you paint it it won't work and the sheeting will then rust from the edges and at any scratches in the paint. If you do not like the colour as Jonon9 says, buy sheets in the colour you want, although these probably won't last as long as the unpainted galvanised sheets you have.

Bluscreendream

Thanks guys for all the info. The store I bought the sheets from don't do pre-coloured sheets so bringing it back is not an option, I am where I am. I'm (painfully) :rolleyes: realising now that an etch primer is the only way to go, that stuff is very expensive though.

I often see large barns with the exact same corrugation done in the red oxide, and I assumed there was a trick or workaround that farmers used to create a grip for the oxide as etch primer for that amount of roofing would be mad expensive. I've heard a lot about a certain industrial paint shop in Tullamore, I think I'll have to pop in to them and see what they can reccomend.

NiallBoo

Bluscreendream wrote: »

I often see large barns with the exact same corrugation done in the red oxide, and I assumed there was a trick or workaround that farmers used to create a grip

I'm fairly sure they just wait 30 years for the sheets to start to corrode then paint it with oxide to slow further corrosion.

Bluscreendream

NiallBoo wrote: »

I'm fairly sure they just wait 30 years for the sheets to start to corrode then paint it with oxide to slow further corrosion.

Would 6 months not do....?

CJhaughey

I used corru galv on a small garden shed instead of Felt which is useless and shortlived.
The shed is up at least 7 years and the roof is still like new.
I wouldn't paint it unless you have to.
In NZ and Australia galv roofs are very common and I am sure they have some ways of painting them economically.

Nekarsulm

If it is still bright and shiny, paint will peel off fairly quickly. It really needs five or six years weathering first, but you can paint now as long as you realise that its not going to last mire than a year or two.

CarrickMcJoe

Use T Wash, it' neutralises the new galvanise before applying the oxide paint. Very easy to apply.

Bluscreendream

Thanks all for the great advice!