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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Painting, Decorating & Tiling Questions >> painting galvanised steel https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1132507803 Message started by sparxxxx on Nov 20^th, 2005, 5:30pm

Title: painting galvanised steel
Post by sparxxxx on Nov 20^th, 2005, 5:30pm

How do you paint galvanised steel its an external location, thanks.

Title: Re: painting galvanised steel
Post by CWatters on Nov 20^th, 2005, 5:56pm

I used gavanised pipe to make poles for the wifes washing line about 4 years ago. Hammerite have a special primer. I think it's latex based. I had problems because the pipes were greasy. Had to clean several times with solvents first.

http://www.hammerite.com/uk/products/ps_special_metals_primer.html

"Promotes adhesion for metal finish paints on non-rusting metal surfaces such as aluminium, galvanized and stainless steel, chrome, brass and copper."

Title: Re: painting galvanised steel
Post by sparxxxx on Nov 21^st, 2005, 5:40am

Thanks CW

Title: Re: painting galvanised steel
Post by hamilton on Nov 21^st, 2005, 7:30pm

Not 100% certain on this, but I think Hammerite primer is for use with hammerite paint, and the second coat has to be applied within a couple of hours, if you leave it longer then you can't repaint it for six weeks or so.

If you want to use ordinary paint (for colour matching purposes), then the galvanised surface needs to be weathered for six months before painting. Then primed with Zinc chromate, followed by your chosen paint system.

If weathering is impractical then degrease and apply a mordant solution to give the surface a key, then apply Calcium Plumbate followed by your chosen paint system.

That's taken me back a few years. ;)

Title: Re: painting galvanised steel
Post by CWatters on Nov 22^nd, 2005, 4:15pm

wrote on Nov 21^st, 2005, 7:30pm:

I let the Hammerite primer dry overnight when I used it. I did two coats of the special primer and two of hammerite top coat. (eg 4 days) The only problem I had was getting the primer to cover initially. In places the galvanised pipe I was using seemed greasy and it was a bit like trying to paint a wax candle with water colour until I cleaned them up. I think I used petrol to get most of it off then hammerite thinners to remove anything the petrol had left. No problem after that.

Title: Re: painting galvanised steel
Post by hamilton on Nov 22^nd, 2005, 5:02pm

Anyway CW, what do you mean by, 'the Wifes washing line?' ;D

Title: Re: painting galvanised steel
Post by sparxxxx on Nov 22^nd, 2005, 7:38pm

Hamilton, thanks very much for your detailed reply. This galvanised steel has been outside for at least six months exposed to the weather but is bright as a new penny.
What is a "mordant Solution" and "calcium plumbate" are there modern equivalents.
I'm looking for a dull brownish finish to blend in with shrubbery trees etc.

Title: Re: painting galvanised steel
Post by CWatters on Nov 23^rd, 2005, 5:11pm

Quote:

Anyway CW, what do you mean by, 'the Wifes washing line?

She rents it to me at quite reasonable rates ;-)

Title: Re: painting galvanised steel
Post by hamilton on Nov 23^rd, 2005, 5:26pm

Oh dear Sparxxxxy,

Talking to another painter today, told him your situation and my solution. He called me a bloody old fart and told me time has moved on, bloody little upstart.

Evidently, Zinnser 123 is the way to go, (I'm sounding like Paintycait now.)

Must put my hands up, I haven't painted galvanised stuff for a loooong while.

Mordant solution is an etching pre-treatment for surfaces like galvanised metal that has not been weathered. After degreasing the surface, you brush on the mordant solution, which will change the colour of the surface, (which also points out any misses), and etches it to give the primer a 'key', wash off and allow to dry; then apply chosen primer.

But bugger all that, get some Zinsser 123 and whack that on. ;)

Title: Re: painting galvanised steel
Post by sailfishoney on Nov 25^th, 2005, 5:15am

wrote on Nov 20^th, 2005, 5:30pm:

How do you paint galvanised steel its an external location, thanks.

first wipe the galvanized steel with vinegar, then I recogmend exterior oil base primer, then top coat with exterior latex. if you do not wipe with vinegar the paint will not stick. the acids in the vinegar nuetralilizes the oils in the galvo

Title: Re: painting galvanised steel
Post by sparxxxx on Nov 25^th, 2005, 6:31am

Thanks everybody

Title: Re: painting galvanised steel
Post by Hitachimad on Dec 3^rd, 2005, 8:16pm

We use an acid (phospheric i think) based etch primer from tikkurila, 'temaprime Mph465'
It is virtually the same as the mordant t washes.

Lightly sand any rough patches or very shiny area, wash with solvent/thinners, brush or spray it on, until the galvy changes to a dull grey, then rinse off with water. When dry it can be painted. :)