A quick question for the experts: I want to paint a steel garage door.
Most of the old paint is intact but some is not. I have given it a
fairly heavy rub down (power tool and wire brush). I have a tin of
primer available. Should I prime the whole door for consistency or is
it better just to spot prime the areas where the paint is missing? The
time involved is not an issue. I just wonder whether paint - primer -
paint is asking for trouble or does primer stick to anything?

Scott wrote:
A quick question for the experts: I want to paint a steel garage door.
Most of the old paint is intact but some is not. I have given it a
fairly heavy rub down (power tool and wire brush). I have a tin of
primer available. Should I prime the whole door for consistency or is
it better just to spot prime the areas where the paint is missing? The
time involved is not an issue. I just wonder whether paint - primer -
paint is asking for trouble or does primer stick to anything?

Just a quick question.

Is the steel, zinc galvanizing ?

If so, that changes the nature of the question.

It's a lot harder to get paint to stick to zinc,
and that's why that question has a different answer.

If the material is just plain shiny flat steel, with
excessive rust capability as a side effect, then the
paint question is a different one. Where the paint
has come off, would have rusted, if it was plain steel.
With a galvanized layer, it won't rust (at least not
right away), but on the other hand, ordinary paint
will not adhere well.

If you don't select the right materials, what happens
is the paint peels off in about a year. I have a galvanized
flashing here, which won't take regular paint. You can
tell by the way the paint film doesn't set up on it,
what's going to happen. Your paint brush can "tell you
a story" sometimes, predicting what's going to happen to
the attempt to get paint to stick. Like, run a paint
brush over surface mildew some time, and see how the
paint "beads" instead of "spreads". And the price you
pay in that case, is early finish failure, if it even
covers at all.

Each material needs more or less prep or process. The
mildew problem is why we clean paint surfaces (or
try to). Like washing with trisodium phosphate, to
get a tooth on the paint (remove enough biological
film so the paint will spread over the real surface).

Applying the paint, is the last and easiest step.
Any joker can paint. Prep requires a genius. There
are plenty of people in this world who will slap
paint on stuff, and then "act surprised" when it
falls off. You can even pay them to do that.

Paul

On Sat, 17 Oct 2020 18:40:50 -0400, Paul
wrote:

Scott wrote:
A quick question for the experts: I want to paint a steel garage door.
Most of the old paint is intact but some is not. I have given it a
fairly heavy rub down (power tool and wire brush). I have a tin of
primer available. Should I prime the whole door for consistency or is
it better just to spot prime the areas where the paint is missing? The
time involved is not an issue. I just wonder whether paint - primer -
paint is asking for trouble or does primer stick to anything?

Just a quick question.

Is the steel, zinc galvanizing ?

I think it's galvanized. There is no sign of any rust.

If so, that changes the nature of the question.

It's a lot harder to get paint to stick to zinc,
and that's why that question has a different answer.

If the material is just plain shiny flat steel, with
excessive rust capability as a side effect, then the
paint question is a different one. Where the paint
has come off, would have rusted, if it was plain steel.
With a galvanized layer, it won't rust (at least not
right away), but on the other hand, ordinary paint
will not adhere well.

This was why I thought about primer.

If you don't select the right materials, what happens
is the paint peels off in about a year. I have a galvanized
flashing here, which won't take regular paint. You can
tell by the way the paint film doesn't set up on it,
what's going to happen. Your paint brush can "tell you
a story" sometimes, predicting what's going to happen to
the attempt to get paint to stick. Like, run a paint
brush over surface mildew some time, and see how the
paint "beads" instead of "spreads". And the price you
pay in that case, is early finish failure, if it even
covers at all.

Each material needs more or less prep or process. The
mildew problem is why we clean paint surfaces (or
try to). Like washing with trisodium phosphate, to
get a tooth on the paint (remove enough biological
film so the paint will spread over the real surface).

I washed with sugar soap then rinsed with a jet wash.

Applying the paint, is the last and easiest step.
Any joker can paint. Prep requires a genius. There
are plenty of people in this world who will slap
paint on stuff, and then "act surprised" when it
falls off. You can even pay them to do that.

I think that is what happened when it was done last time by
contractors appointed by the managing agents.

Scott wrote:
On Sat, 17 Oct 2020 18:40:50 -0400, Paul
wrote:

Scott wrote:
A quick question for the experts: I want to paint a steel garage door.
Most of the old paint is intact but some is not. I have given it a
fairly heavy rub down (power tool and wire brush). I have a tin of
primer available. Should I prime the whole door for consistency or is
it better just to spot prime the areas where the paint is missing? The
time involved is not an issue. I just wonder whether paint - primer -
paint is asking for trouble or does primer stick to anything?
Just a quick question.

Is the steel, zinc galvanizing ?

I think it's galvanized. There is no sign of any rust.
If so, that changes the nature of the question.

It's a lot harder to get paint to stick to zinc,
and that's why that question has a different answer.

If the material is just plain shiny flat steel, with
excessive rust capability as a side effect, then the
paint question is a different one. Where the paint
has come off, would have rusted, if it was plain steel.
With a galvanized layer, it won't rust (at least not
right away), but on the other hand, ordinary paint
will not adhere well.

This was why I thought about primer.

Try keywords like "wash primer".

I've not used any, because I'm the guy with the galvanized
surfaces with no paint on them :-) I can tell you with
authority, that regular paint lasts around a year,
before the lack of adhesion makes it come off again.

Something is required to get a "tooth" on the material.
Otherwise, with regular paint, the zinc reacts with the
organic content a bit. The purpose of the primer, is to
not allow that reaction, and provide some isolation.

The wash can be acidic, as one means of building a primer.
And a concern would be if the acid part bleeds through
the next layer of paint or not. And the primer has to
cover the metal part, as you don't want to be seeing any
metal where the regular paint goes on top.

Paul

On Sun, 18 Oct 2020 09:58:20 -0400, Paul wrote:
Try keywords like "wash primer".

I've not used any, because I'm the guy with the galvanized surfaces with
no paint on them :-) I can tell you with authority, that regular paint
lasts around a year,
before the lack of adhesion makes it come off again.

Hmmm... we had new railings put up around 4 years ago. They were
galvanised and spray painted before fitting. Nothing special about the
paint other than it being thinned to be able to spray it. Apart from
weathering of the paint its still sound. They are ready for a paint next
year though.

Bev Wrote in message:
On Sun, 18 Oct 2020 09:58:20 -0400, Paul wrote:
Try keywords like "wash primer".

I've not used any, because I'm the guy with the galvanized surfaces with
no paint on them :-) I can tell you with authority, that regular paint
lasts around a year,
before the lack of adhesion makes it come off again.

Hmmm... we had new railings put up around 4 years ago. They were
galvanised and spray painted before fitting. Nothing special about the
paint other than it being thinned to be able to spray it. Apart from
weathering of the paint its still sound. They are ready for a paint next
year though.


Did you see them spraying? Or is it in fact powder coat?
Mordant solution is sposed to prep new zinc for paint. I've had
mixed results tho...
--
Jimk


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On 18/10/2020 10:09, Scott wrote:


I think it's galvanized. There is no sign of any rust.

Zinsser Bulls Eye 123 primer.

I've used this successfully with a variety of undercoats/gloss both
water and solvent base.


https://www.zinsseruk.com/product/bulls-eye-1-2-3/
Available from Screwfix and Toolstation (often a 10%+ difference in price)

technical details
https://www.zinsseruk.com/core/wp-co...mer-Sealer.pdf

How to paint galvanised...

https://www.zinsseruk.com/howto/paint-galvanised-metal/

Obviously they are recommending their own paints after a 123 primer but
it seems to work well with any paint I've used on top of it.




--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 18/10/2020 21:18, alan_m wrote:
On 18/10/2020 10:09, Scott wrote:


I think it's galvanized.Â* There is no sign of any rust.

Zinsser Bulls Eye 123 primer.

I've used this successfully with a variety of undercoats/gloss both
water and solvent base.


https://www.zinsseruk.com/product/bulls-eye-1-2-3/
Available from Screwfix and Toolstation (often a 10%+ difference in price)

technical details
https://www.zinsseruk.com/core/wp-co...mer-Sealer.pdf


How to paint galvanised...

https://www.zinsseruk.com/howto/paint-galvanised-metal/

Obviously they are recommending their own paints after a 123 primer but
it seems to work well with any paint I've used on top of it.





I would spot prime the patches first with 123 then when dry in 1 hour
apply a coat of 123 over the whole door. This paint will stick well to
previous gloss, providing that the old paint is sound, and give a
somewhat mat keyed finish for the next coat of paint. At both points
check if the old paint was feathered enough at the edges and/or if the
finish so far is acceptable to you. The paint is not a filler and any
sharp raised edges between the sanded areas and existing paint is likely
to show in the final cot of paint.

If you have sanded through the galvanisation 123 is also claimed to be a
rust inhibiter.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 18/10/2020 21:41, alan_m wrote:
On 18/10/2020 21:18, alan_m wrote:
On 18/10/2020 10:09, Scott wrote:


I think it's galvanized.Â* There is no sign of any rust.

Zinsser Bulls Eye 123 primer.

I've used this successfully with a variety of undercoats/gloss both
water and solvent base.


https://www.zinsseruk.com/product/bulls-eye-1-2-3/
Available from Screwfix and Toolstation (often a 10%+ difference in
price)

technical details
https://www.zinsseruk.com/core/wp-co...mer-Sealer.pdf


How to paint galvanised...

https://www.zinsseruk.com/howto/paint-galvanised-metal/

Obviously they are recommending their own paints after a 123 primer
but it seems to work well with any paint I've used on top of it.





I would spot prime the patches first with 123 then when dry in 1 hour
apply a coat of 123 over the whole door. This paint will stick well to
previous gloss, providing that the old paint is sound, and give a
somewhat mat keyed finish for the next coat of paint.Â* At both points
check if the old paint was feathered enough at the edges and/or if the
finish so far is acceptable to you.Â* The paint is not a filler and any
sharp raised edges between the sanded areas and existing paint is likely
to show in the final cot of paint.

If you have sanded through the galvanisation 123 is also claimed to be a
rust inhibiter.


Oh - and wear disposable gloves as 123 can be a PITA to get off skin
once dried (and it dries fast). A green pan scrubber lubricated with
plenty of washing up liquid will held remove it from skin.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On Sun, 18 Oct 2020 21:18:07 +0100, alan_m
wrote:

On 18/10/2020 10:09, Scott wrote:


I think it's galvanized. There is no sign of any rust.

Zinsser Bulls Eye 123 primer.

I've used this successfully with a variety of undercoats/gloss both
water and solvent base.

I take it red oxide would be a mistake then, on a metal that seems not
to be prone to corrosion (presumably because it's galvanised)?

It would be worth it if you can get hold of a hot air gun, it will strip easily.
Then use Hammerite Special metals primer and a couple of coats of gloss. It will last for years.

Is there any rust? If yes then some of that rust inhibitor sealer stuff is
good. I think prime it all myself, if you cannot get down to base metal,
then its not going to come off.
Brian

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"Scott" wrote in message
news
A quick question for the experts: I want to paint a steel garage door.
Most of the old paint is intact but some is not. I have given it a
fairly heavy rub down (power tool and wire brush). I have a tin of
primer available. Should I prime the whole door for consistency or is
it better just to spot prime the areas where the paint is missing? The
time involved is not an issue. I just wonder whether paint - primer -
paint is asking for trouble or does primer stick to anything?

Scott wrote:
A quick question for the experts: I want to paint a steel garage door.
Most of the old paint is intact but some is not. I have given it a
fairly heavy rub down (power tool and wire brush). I have a tin of
primer available. Should I prime the whole door for consistency or is
it better just to spot prime the areas where the paint is missing? The
time involved is not an issue. I just wonder whether paint - primer -
paint is asking for trouble or does primer stick to anything?


Get a primer for zinc it is almost certainly zinc plated and clean with
acetone or similar before applying.

Thanks for the suggestions to use Zinsser. The job finally started
this morning. At first I thought the Zinsser was a bit thin. However,
when I discovered how difficult it is to remove from my hands, I am
now reassured that the grip is impressive.