Thread: Rust removal from roofing - wire brush and pressure wash, or skip the brushing?

Unless you kill/remove the rust and just cover it; it will rust from the inside out. How do I know; I have a car in the workshop with that problem.

Ken

Penetrol claims to stop the rust by excluding all air by penetrating right in. Guy in the hardware used to be a painter and said he preferred that to FerroPro or Kill Rust etc (which is what I went in looking to buy) so I accepted his advise.

You don't think it's the right way to go Ken?

Do you also believe in alcaminy.
I thinks that's how you spell it lol
Rust is rust the only way to get rid of it is to cut it out if it's serious or rub back hard with 60 grit sandpaper it's just brown surface.
So Brett there's no easy way out.
I spent 15 years cutting rust out of cars.
Rub it back hard then treat with rich zinc primer straight away
Metal loves to rust oxerdise more than anything

This is what they have to say:
http://www.floodaustralia.net/produc...-anti_rust.php

I'll be following it up with a primer and then a couple of coats of Solaguard or similar.

FF

I am very sceptical about the claims of the 'snake oil' salesman.

As Simplicity said; the rust has to go; either cut out and replaced or if there is sound metal behind it; mechanically remove the loose shale then then chemically treat (rust buster, phosporic acid etc) to kill all traces in the pores of the steel then the zinc rich primer; maybe cold gal.

I have found that the rustbuster etc if allowed to dry forms a skin of black rust which will eventually corrode and become the dreaded red rust. I have found that keeping the rust area wet with the rust buster until it has done its job and then using a rag to wipe off the surface and let dry before the zinc rich paint has worked for me.
'Tin cancer' is a good name for red rust.

Ken

I just had a read of the Penetrol blurb Brett and I think it should do the job nicely for some bits of roof iron.
I'd just P/Wash and slop some paint laced with penetrol on the rusted bits. Or just Penetrol and paint later.

Yeah, it's hard to know. eh? I've dealt with the guy in the hardware before and he seems like a straight shooter. Mind you, what he was saying was quite counter-intuitive to me, but, he's the pro painter, not me.

I did a bit of a search to see what people think of it. One guy in Florida said he had a metal sculpture in the garden that was rusty - gave it the Penetrol and nothing else and it lasted about 9 months before the rust reappeared. That's not too bad considering he didn't apply anything else over it, which is what is supposed to happen. He says the atmosphere is bad where he is, so I presume close to the coast.

It'd be interesting to hear from people who have used Penetrol, to see what they make of it.

Brett,
My experience with mechanical wire brushing is that it takes off the loose stuff and puts a glaze over the rust. Good you say.....well that glaze is still active rust and will start up again under what paint you put on top. Alternatively.....to use a mechanical sander cuts off the rust and reveals bright shiny metal that is "too slippery" to keep the undercoat on. I have, in the past, given the rust a good sanding but left the surface "scratched" to give the undercoat and subsequent coats something to grab hold of.

Originally Posted by chambezio

mechanical wire brushing takes off the loose stuff and puts a glaze over the rust. Good you say.....well that glaze is still active rust and will start up again under what paint you put on top

Understood Rod, and that glazed layer is what would normally be then acted upon by Ferropro et al. This is what I envisaged when i went to the hardware.

However, Penetrol maintain that the rust can't start up again because there is no residual air left - pushed out by the Penetrol. I mean, the theory sounds ok, but......

If it's that good, I guess nobody in areas dealing with rust would ever bother cutting out rust, and would instead slap on a coat of this stuff and call the job good to go

Originally Posted by Pete F

If it's that good, I guess nobody in areas dealing with rust would ever bother cutting out rust, and would instead slap on a coat of this stuff and call the job good to go

Well yeah, that's what they are more or less saying Pete, and they reckon it's big in the shipping industry. Beats me.

When we dealing with rust on auto restorations.
If I found an area about the size of 5 centre au piece we cut out and replaced a cigaret pack size of metal on average
The cost for that a proffesional auto shop say $100 au
These rust treatments sell because of power of economics.
But Brett if u follow the ideas given here and this tin lasts another 5 years and your outlay is say $150 all up u can't loose.
Has for them using it on boats of course they will if they save thousands on repairs for the boat being sea worth for another two years that's a lot of money saved

Can you slit the iron down lengthways cutting out the rust....

I like using duragal paint these days..

I've ended up with a relative pile of phosphoric acid here ... it was a "gentle cleaner" for the salt-water pool 'element'.

BobL has used phoz on things ... he might have an opinion.

A car is different to a roof, I think ... has water coming up and around from everywhere, and getting trapped with dirt etc ...

I would have thought the paint does the job of excluding water and oxygen ...

Cheers,
Paul