Rust on Colorbond roofing

[kermac]

Hi   I have a Colorbond roof on my house. I guess it would be around 30 years old. Inland, dry area (until recently!).  Some years ago I had a Solahart roof-mounted water heating system installed. On very hot days it vents large amounts of hot water directly onto the roof, which runs down one of the channels in the Colorbond and from there into the gutter. Our local mains water is very mineral-rich, and leaves nasty stains on everything.  I noticed the other day the channel where the vented water runs down has become quite rusty, in fact the rust is starting to eat through the metal.  Parts of the gutter and most of the downpipe are also in bad shape.  My guess is that the installer should have connected a copper pipe to the vent and led it down the channel to protect the roofing iron, but it's a bit late for that now.  My question is how should I tackle this short of the replacement of the entire roofing panel?  Presumably remove the rust first with a wire brush, but is there a suitable product which I can paint all the way down the channel to protect it from further corrosion?   Thank you.   KM

[EricL]

Hello @kermac

Welcome to the BUnnings Workshop community. It's fabulous to have you join us, and thank you for sharing your question about your Colorbond roofing.

I suggest having a quick look at this discussion - How to seal holes in rusty galvanised roofing? by @RipVanCutter. The general procedure is to remove as much of the rust as you can and then use the Ranex rust converter. Ranex Rustbuster converts rust from a detrimental oxide to a beneficial phosphate of iron. Once the roof is totally dry, I suggest applying Crommelin 1L Exterior Grade Brushable Waterproofer in combination with Bond breaker tape. For the more critically damaged areas, I propose using Consolidated Alloys 100mm x 10m Weatherproof Byute Flash Flashing Tape.

It's important that when you attempt this repair the area must be totally dry and the roof must not get rained on for the next several days. Once you've done the repair, I suggest thinking back to your proposal of attaching a copper pipe to the vent to prevent damaging your roof 

If you need further assistance, please let us know.

Eric

[kermac]

Hi Eric

Thank you so much for your helpful reply to my problem. I wonder if this solution is equally applicable to my Colorbond roofing? I'm guessing Colorbond may be treated differently to galvanised?

Thanks again

kermac

[EricL]

Hello @kermac

Thank you for telling me about your Colorbond roofing. It was indicated in fine print that Ranex is not compatible with Colorbond roofing. What I suggest after the repair is thinking about future prevention. Once you've repaired the damage on your roof, I suggest putting in that copper diversion pipe to prevent the hot water from landing on your roof.

If you need further assistance, please let us know.

Eric

[Noyade]

G'day Eric. @EricL 

"The general procedure is to remove as much of the rust as you can and then use the Ranex rust converter."

Photos below.

I went to Inspirations Paint a few months ago and spoke with the manager about a section of my roof. Without any prompting from me he started to rant on about rust converter "being the worst thing you could possibly apply to rust on roofs."

No idea why (I didn't question him) and in the end all he offered was advice on how to clean the rust off (physically) and then to use the undercoat shown.

Any thoughts on why he would have felt that way?

Either way - it's gonna be a very long time before I'm physically able to get back to the roof.   ☹️

[EricL · Accepted solution]

Hello @kermac

It's great that @Noyade has brought up a very good point. My apologies for recommending Ranex on Colorbond roofing. It's not compatible with Colorbond, I've spoken with the paint specialist at the paint department and it's better to sand the rust off the roof. Once you've cleaned and removed as much of the rust as you can, I suggest using the White Knight 1L Rust Guard Quick Dry SLS Etch Primer Paint. I also recommend using the White Knight Rust Guard Gloss White Epoxy Enamel Paint for your top coat tinted in the colour of your choice. 

If you have any other questions we can help with, please let us know.

Eric

[kermac]

Thanks again Eric! I'll be getting into this in the next few days.

Kerry