Primer for galvanised steel window and putty?

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Would appreciate advice on choice of suitable primer...

I painted a Crittalls window (i.e. zinc galvanised steel) last year using this Rustins water-based paint as a primer:

Quick Dry Galvanised Metal Primer | Rustins

A quick drying, low odour metal primer that is suitable for indoor and outdoor use. Containing anti-corrosion additives it is ideal for use on bare...
www.rustins.ltd www.rustins.ltd

But I didn't like the way the paint went on (oddly foamy). Also, seems to chip easily, though I added two top coats of Johnstone's metal paint to the exposed/outer frame surfaces.

I'm currently renovating another Crittalls window only this time I've had to replace the putty too. I understand that I can't use a water-based paint on the linseed oil-based putty - and I'm not keen on using the Rustins paint anyway. I'd prefer to use just a single primer, if that's possible. Can anyone recommend a suitable oil-based primer that's good for both galvanised metal and putty? Thanks.
 
Not convinced you can use any paint/primer on the putty. The oil in the putty will fail it. What I do is use a bead of hybrid polymer sealant on top of the putty. The bead will adhere to the glass as well as the frame. You should have used sealant in place of the putty. But, that takes someone brave enough to experiment, and someone who has some feel for materials. Sealant as a substitute for putty worked for me. Hybrid polymer is paintable. If the paint fails on the glass side of the bead, the sealant is water proof.
 
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Interesting, inventive approach.

Prior to starting this renovation, I noted that rainwater had indeed seeped down the slither-of-a-gap between old putty and glass pane - probably accounts for why some of the old putty wasn't firmly held in place. But then it's been at least 30 years since the windows on the outbuilding were last painted or had putty replaced and these windows must be well galvanised because there's no hint of rust on the frames.

I've been "researching" the issue of a suitable primer. Very little definitive info for the DIY'er out there for (zinc) galvanised steel primers (and some info is contradictory) bit it seems to me that a zinc phosphate oil-based primer is my best bet, however, It's quite expensive and most suppliers sell it in larger quantities than I need. May stick with the Rustins water-based primer after all.
 
If you use screwfix multi purpose glazing putty you might find it not too oily. Back in the day metal glazing putty was pale blue and not as oily as lin. oil stuff
 
You prime the frame first, and gloss at least the rebate. You can gloss the whole frame before puttying in the glass.

After applying the putty, leave it to lose its surface oiliness and to harden somewhat before applying a coat of oil based gloss to it.

There is probably a modern glazing compound suitable for metal frames, but they are now so rare I have not looked
 
JohnD said:
After applying the putty, leave it to lose its surface oiliness and to harden somewhat before applying a coat of oil based gloss to it.
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I have 30 year old linseed putty that zinsser 123 cannot adhere to. That's on the interior side, so I don't care
 
Here's 30 year old linseed putty under paint, under unpainted sealant. Pro windowers can't match this. my seals could be renewed if there is a need. Timber window.

sealant.png
 
DiyNutJob said:
I have 30 year old linseed putty that zinsser 123 cannot adhere to. That's on the interior side, so I don't care
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"After applying the putty, leave it to lose its surface oiliness and to harden somewhat before applying a coat of oil based gloss to it."


I believe zinsser 123 is alcohol based, not oil based. And is not gloss.
 
DiyNutJob said:
Here's 30 year old linseed putty under paint, under unpainted sealant. Pro windowers can't match this. my seals could be renewed if there is a need. Timber window.

View attachment 282668
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I was under the impression that linseed oil based putty should not be used with double glazed units. AFAIK it doesn't allow the DGU to expand and contract properly. That said, your DGUs have lasted 30 years...

Your putty bead must be, what, 1 or 2mm deep?

BTW, when faced with linseed oil based putty that has a hairline gap where it meets the glass, I too use an MS polymer, as I do if reglazing the whole window. You need to use waterbased paint to prime most MS polymers though. Oil based paint, directly, over most of the MS polymers that I have used stays tacky for months, even if you wait months before applying the paint.
 
opps said:
I was under the impression that linseed oil based putty should not be used with double glazed units. AFAIK it doesn't allow the DGU to expand and contract properly. That said, your DGUs have lasted 30 years...

Your putty bead must be, what, 1 or 2mm deep?

BTW, when faced with linseed oil based putty that has a hairline gap where it meets the glass, I too use an MS polymer, as I do if reglazing the whole window. You need to use waterbased paint to prime most MS polymers though. Oil based paint, directly, over most of the MS polymers that I have used stays tacky for months, even if you wait months before applying the paint.
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When I replaced the putty with sealant, the sealant width was that of a pound coin because I used the coins to set the gap. The original width must be close to that.

I only paint after priming. No idea what happens if unprimed. Hybrid polymer does react with oil based paint and turns yellow. The sun washes it white again. I only have water primer now. If I use oil based, that will add 2 extra days for any paint job. I go 2x primer and 3x gloss for exterior painting.

When I paint hybrid polymer, I let it cure 24 hours and then prime and paint. I found no problems with that. The sealant beads on my windows are not painted. They might be painted in the future if there is need for repair. I don't see the sealant failing. The paint under it might.
 
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I learned linseed puttying as a youngster, haven't touched it for years.
 
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