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

[FenceFurniture]

I've scored some used Cliplock roofing that I intend to replace my shed roof with.

There is some significant surface rust in on of the two channels on each length, and my process so far has been to run over it with a rotary wire brush in a drill, pressure wash it and then coat with Penetrol.

I'm wondering how necessary it is to do the wire brushing, as it adds a significant step in the treatment of each length, and is rather noisy for the neighbours. Just now I went straight to pressure washing on one length without brushing it, and there is no loose rust, and it doesn't stain my finger when I rub it.

What say the brains trust please? Continue wire brushing or just proceed straight to the pressure wash?

[Toggy]

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

[FenceFurniture]

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?

[Simplicity]

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

[FenceFurniture]

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

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

[Toggy]

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

[NCArcher]

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.

[FenceFurniture]

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.

[chambezio]

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.

[FenceFurniture]

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 topUnderstood 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......

[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 :wink:

[FenceFurniture]

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

[Simplicity]

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

[.RC.]

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

I like using duragal paint these days..

[pmcgee]

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

[BobL]

Phos converts the rust from oxide (red stuff) to a scaly phosphate (blue black) which is inert (does not keep rusting) but not impervious to air so unless it is covered with something impervious to air it will eventually rust again. A

The problem with phos is it should not be used on galv because it dissolves the galv! :oo:

I have two galvanised rusting sea containers that I have tried various treatments out on.
In the end I gave up and painted the rusty patches with several coats of bituminous paint.
It's horrible stuff ftp apply but it seems to be working.

[FenceFurniture]

Cheers Bob. Given that it is galvanised roofing it's just as well I didn't get the Phos.

I put another thread up to see if anyone has ever used Penetrol, but no bites, so I guess I'm the forum guinea pig on Penetrol.

I'll get back to yez in a few years and let yez know how it goes. :D

[FenceFurniture]

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 http://d1r5wj36adg1sk.cloudfront.net/images/smilies/standard/wink.gif


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.


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


Do you also believe in alchemy?
So Brett there's no easy way out.

Bah! http://d1r5wj36adg1sk.cloudfront.net/images/smilies/anoyd.gif All you nay-sayers. http://d1r5wj36adg1sk.cloudfront.net/images/smilies/sad/sneaktongue.gif :D At last we have a user of Penetrol for stopping rust:
http://www.woodworkforums.com/showthread.php?t=189101&p=1816981#post1816981

Applied some 4-5 years ago, and still no-rusty. YEEHA! (mainly because I have completed the Penetrol prep).

:hpydans:

[Bushmiller]

For all you doubting Thomases see my reply here :D :

http://www.woodworkforums.com/showthread.php?t=189101

Frankly, I can't speak highly enough of it. I use it all the time (no, make that only when I'm painting :rolleyes:).

My only question was why did't they put it in oil based paint first up? I think the answer to that is that the paint goes off quicker. If you are using it as an additive to oil based paint, just make up a mix sufficient for that job. Also only buy enough to be used in a reasonable period of time. It does go off if exposed to air for a long period of time. How long? More than six months perhaps with say the tin half empty, but that is an approximation.

I would never bother with the "kill rust" "phosphoric acids" etc ever again. (Qualification to that is that, regrettably, it is not compatible with automotive paints.

Regards
Paul

PS: All the usual disclaimers, but if anybody wants to send me large sums of money in recognition of my endorsement I am very happy to supply bank details. Please PM me without delay :wink: .

[Vernonv]

I've had success with Penetrol as a rust preventer. About 5 years ago I purchased a Landcruiser that was previously used for beach recovery work ... hence it had a lot of rust in it.

I cut out all of the "bad" rust and replaced it with new steel, however there was a lot of minor surface rust in areas such as the inside of the bottom of the doors, etc. I thoroughly cleaned out these areas and applied a liberal coating of Penetrol. I also sprayed Penetrol (with an engine cleaning gun) into areas such as the inside of the sills and the chassis rails.

After all this time, no rust has developed in the areas that I treated and when I last had one of the door skins off, it looked the same as when I treated it all those years ago i.e. no progression of the rust.

A couple of points:
1. Only surface rust was treated i.e. not bad flaky rust.
2. The areas I treated are not exposed to UV.

[Simplicity]

Immmmmmmm lol

[soundman]

EEeeverybody is looking for a cheapand easy solution to rust.

There are heaps of products on the market that offer a low effort solution...because that is what people want to hear.

Fact is there is not one that is long term AND cheap AND easy in a 100% weather exposed situation.

start withe the pressure washer.....there are high pressure industral pressure washers that will take rust and anything else back to bright bare metal.

They are very commonly used in heavy industry and minning.....A mate's son is cerified to use one.......they will also cut the end off you boot toes and all.....they won't let you near one without the certification.
He is an indiustrial painter, he has used these monsters on a few oil rig and mine trips...they just take everything off heavy steel work..rust, paint, oil, marine growth anything not realy firmly attached.

In the roof restoration business they use "slightly less vigorous" pressure cleaners that remove the vast majority of rust leaving only the lightest residue....a residue light enough that the chemical agents in the paints that follow can deal with.

In general the paint supplier will specifiy the required output of the pressure cleaner.......that is if you want the 10 year paint manufacturer warranty.

There is a new generation of roof paints out there specifically designed to deal with this exact issue.......they may not be cheap...but the good ones are spactacularly effective.
Some of the latest ones are water borne, self primming, single pack epoxies.

They react with the surface....converting or stabilising any corrosion, etch to any bare metal and key very agressivly with just about anything.....then the set up very hard and bright..and seal out moisture.....being water borne, slight moisture in or on the surface is not an issue because it is reacted........singularly spactular products.

Some of them even have thermal barrier technology included......the latst thing is dichroic pigments......pigments that show their colour by reflecting light and heat out of the surface.....one supplier claims their black thermal barrier paint is as cool as conventional white.

I have not used any myself...but I have been on a few roofs that have been treated...very impressive.

Got a roof to do myself.....that is the way I will be going.

Receene have a new generation roof paint that is suposed to be $#!Thot.

One thing these products don't like is oil.

There are some other priducts that claim to stabilise all but flakey rust....some of the better ones suceed.....but they are not cheap or pleasant to use.

POR15 has been arround for a very long time, and they have products for sorting out corrosion in a number of situations..including inside fuel tanks.

as for the rest.
Well...some of them work modestly, but to be at all effective long term they depend on some sort of long term durable finish over them.

SO..do you want to fiddle with a stop gap solution or do a propper job.

Buy one of the current technology roof paints, hire a beefy pressure cleaner and it will probably be cheaper and easier..AND a better job.

cheers

[Oldneweng]

EEeeverybody is looking for a cheapand easy solution to rust.

There are heaps of products on the market that offer a low effort solution...because that is what people want to hear.

Fact is there is not one that is long term AND cheap AND easy in a 100% weather exposed situation.

start withe the pressure washer.....there are high pressure industral pressure washers that will take rust and anything else back to bright bare metal.

"SNIP"

SO..do you want to fiddle with a stop gap solution or do a propper job.

Buy one of the current technology roof paints, hire a beefy pressure cleaner and it will probably be cheaper and easier..AND a better job.

cheers

I like the sound of these roof coatings, but it is my experience that the worst rust is often underneath the joints. This is the case with my 60 year old roof. What happens here?

Dean

[soundman]

Well ya can't polish a ......

cheers

[Oldneweng]

Well ya can't polish a ......

cheers

Yes, well I find good advice hard to find these days. :rolleyes:

Dean

[soundman]

well seriously...the practicalities or treating rust under the laps of a roof sheet simply are not there.

There are all sorts of pacth ups that people would have done in the past.....and that is what they where..patch ups.......but nobody bothers these days.

Most roof work these days is done in continuous sheets ridge to eave..either ordered to size or rolled on site.

Thus the problem with rust and leaks between the laps are solved.

cheers