Paint blistering galvanized corrugated tin roof

[Geoffreywrc]

I've a wagon roof shed. ( old army shed)
Problem is it's really old tin but in very good shape as current tin is thin etc
Have painted this probably 4 times each time power hosing loose paint off but after couple years paint keeps blistering off in places.
Would it be an idea to blast this roof completly to get all old paint off and create a rough surface on tin to get a primer to stick to and then come over with a top coat.
Any other ideas out there
Picture

in attachment

 

[grainboy]

In my experience of grain bins, you will never get paint to stay on galvanised steel,
Why would you want to paint it in the first place ?

 

[Geoffreywrc]

In my experience of grain bins, you will never get paint to stay on galvanised steel,
Why would you want to paint it in the first place ?

As it's really old corrugated tin it has started to rust on outside so was painted years ago. Old corrugated tin is however far better quality tin than that of today, you'll know as soon as you lift a sheet of it, its twice as heavy as what you would buy today, even the thickest of today's tin.
On the inside of the roof it's as fresh and as good as the day it was fitted.

 

[24/7 farming]

Is the paint ur using for use on galvanised surface?, makes a big difference in my experience of using some, of course u pay dearer for it, but not really in the long run. Have used the hamerite version here a few times

 

[solo]

Grain store built in 1968 with 3” currugated tin sides has been painted by hand brush a few times now. After removing loose rust and paint the best covering I have used is coal tar paint. It still looks like new after 25years. It was very hard work to apply by brush. ( a bit like cold thick treacle)?Rest of the shed I used bitumastic which lasted about 10 years. Not easy to apply but lasted reasonably well. Whole building was done with Bedec barn paint about 6 or 7 years ago. This was easy to apply and has lasted well so far. It will be my first choice to use when next required. This is my experience from side cladding.

 

[Steevo]

I'd just skin it with a layer of plastic coated tin set above a suitable air gap to prevent potential for rust. Would look tidy forever more then.

 

[Sid]

I've a wagon roof shed. ( old army shed)
Problem is it's really old tin but in very good shape as current tin is thin etc
Have painted this probably 4 times each time power hosing loose paint off but after couple years paint keeps blistering off in places.
Would it be an idea to blast this roof completly to get all old paint off and create a rough surface on tin to get a primer to stick to and then come over with a top coat.
Any other ideas out there
Picture

in attachment

The paint isn't expanding and contracting at the same rate as the roofing sheets.
Causes fractures.

 

[averageguy54]

Galvanized metal needs special preparation before painting. Google "painting galvanized metal" and you will find good directions to make our paint stick. The one by American Galvanizers is very helpful. I'd give you a link but it's beyond my technological skill set I'm afraid.

 

[Steevo]

Galvanized metal needs special preparation before painting. Google "painting galvanized metal" and you will find good directions to make our paint stick. The one by American Galvanizers is very helpful. I'd give you a link but it's beyond my technological skill set I'm afraid.

Mordant solution

 

[deleted user 837354]

There is a certain primer you need for galv I thought? Best check it is compatible with the top coat as well mind.

 

[Godber]

Grain store built in 1968 with 3” currugated tin sides has been painted by hand brush a few times now. After removing loose rust and paint the best covering I have used is coal tar paint. It still looks like new after 25years. It was very hard work to apply by brush. ( a bit like cold thick treacle)?Rest of the shed I used bitumastic which lasted about 10 years. Not easy to apply but lasted reasonably well. Whole building was done with Bedec barn paint about 6 or 7 years ago. This was easy to apply and has lasted well so far. It will be my first choice to use when next required. This is my experience from side cladding.

Bedec Farm paint is good and long lasting on the galvanised surfaces but not good enough where rust is showing in my experience. Rusty bits need treating first

 

[gorgous]

Bedec Farm paint is good and long lasting on the galvanised surfaces but not good enough where rust is showing in my experience. Rusty bits need treating first

Any recommendations on how to treat the rusty bits?

 

[Hooby Farmer]

Grain store built in 1968 with 3” currugated tin sides has been painted by hand brush a few times now. After removing loose rust and paint the best covering I have used is coal tar paint. It still looks like new after 25years. It was very hard work to apply by brush. ( a bit like cold thick treacle)?Rest of the shed I used bitumastic which lasted about 10 years. Not easy to apply but lasted reasonably well. Whole building was done with Bedec barn paint about 6 or 7 years ago. This was easy to apply and has lasted well so far. It will be my first choice to use when next required. This is my experience from side cladding.

We have a double round roof shed the exact same here. Built in 1967 tin is like new like yours it has been painted on the outsides a few times but unfortunately the timbers are starting to rot.

 

[essexpete]

What do they use on pylons?

 

[milkloss]

What do they use on pylons?

pylon paint.......



no, seriously, they use a yellow/beige primer first, got a few cans here if anyone wants the label.

 

[Sid]

pylon paint.......



no, seriously, they use a yellow/beige primer first, got a few cans here if anyone wants the label.

Would that be an option on the roof? to pile on the paint?

 

[Steevo]

Would that be an option on the roof? to pile on the paint?

Pylon and “pile on” are two totally different things.

 

[Exfarmer]

Trouble is you are never going to get all the old paint off so using a galvanising primer is a waste of time

 

[Teejay]

When they paint pylons they only give it a wire brush to get rid of the loose paint, then put more primer on followed by top coat.

 

[Gordy1]

I've a wagon roof shed. ( old army shed)
Problem is it's really old tin but in very good shape as current tin is thin etc
Have painted this probably 4 times each time power hosing loose paint off but after couple years paint keeps blistering off in places.
Would it be an idea to blast this roof completly to get all old paint off and create a rough surface on tin to get a primer to stick to and then come over with a top coat.
Any other ideas out there
Picture

in attachment

Paint on galvernised tin, metal pipes etc will peel off as the galvanise has to breath I was told.