Primer for cast iron guttering

[BlueTed]

Morning All. I know guttering has come up many times on here but I cannot find an answer as to which primer is best. I’m taking the guttering down and replacing some parts that are beyond repair with reclaimed sections. I have read conflicting advice (on the internet) about if red oxide or zinc primer is best for cast iron guttering?
Also, presumably there is no way/reason to try and coat the inside of downpipes?!

 

[CliffordPope]

Genuine red-lead oxide is the traditional thing. It apparently has a unique way of bonding to cast iron that no other primer can match.

 

[Feltwell]

Someone asked a very similar but broader question on an old thread, here was my reply:-

I've done a fair bit of reusing old cast iron gutter here - sourced on Ebay - plus a bit of new stuff, so here would be my advice:-

Old guttering varies in size, half round 5" from one manufacturer won't always fit well with half round 5" from another manufacturer, so be careful. I've got 4 1/2" gutter that fits nicely with some 5" I got from elsewhere!

Wire brushing - doesn't do much I find, a cup brush on an angle grinder really didn't take much off, just polished the rust! I used a needle scabbler with a compressor, worked a treat, but it's NOISY!! (to put it mildly!). If you can get a compressor from somewhere, a decent size one, then an air hammer with a needle scabbler attachment is only about £25 or so. Aldi sell them on offer every now & then, believe it or not!

Shotblasting - I have a foundry not far away that makes guttering, the firm that does blasting for them reckons about 10% fail during blasting, on used stuff he reckoned that could be as high as 50%. He'd do the job for me if I wanted but strongly advised me not to bother.

Cutting - an angle grinder, preferably a 9" one, is the only way to go. Oddly, I found that diamond discs intended for cutting stone worked best. Don't forget that as your cut end is usually going inside a socket it doesn't have to be a perfect cut.

Fall -what you're saying there sounds a bit light to me, bit more gravity required!

Paint - I used 2 (or was it 3?) coats of cheap Screwfix own brand black metal paint straight onto the metal, inside and outside of the gutters. The first gutters I did (about 10 years ago) still look fine. If you look at old guttering that is rusting through, it's not the inside as such that rots - it's the back, where it's against the fascia boards and no one ever paints the outside as you can't see it. Painting inside the downpipe?? Definitely not - it's rare for downpipes to rust through anyway, it's the guttering that fails first. Downpipes are usually pretty thickwalled, majority of mine are original to the house even now.

Jointing gutters - don't bother with linseed putty, eventually it goes hard and can cause leaks as the gutters expand and contract. Roof and Gutter seal, that comes in silicone sealant type tubes, is a black tarry substance that says flexible permanently and works very well for gutter joints. Use inside the sockets prior to offering them together, then smear what squeezes out inside the gutter to fill the gap. It's cheap as well. One area where modern sealants are best!

Drilling holes for bolts to join sections - get a pack of cheap HSS drill bits from Screwfix or similar, drill slowly, and I keep a spray bottle of oil/water emulsion that I spray on as a cutting fluid. Works for me. Be prepared to sharpen the bits or (they are cheap in packs of 10) buy enough so that after 2 or 3 holes you throw them away.

Bolts - roofing bolts are cheap and work fine - like this:- http://www.screwfix.com/p/easyfix-roofing-bolts-bright-zinc-plated-m6-x-20mm-10-pack/5213j

Downpipe joints, be it at fittings or just straight joints - don't seal with anything, if the downpipe blocks then water will back up to the next joint and leak out, so you know where the blockage is. Just tap (gently!) three little bits of folded roofing lead into the joint to centre the pipes, stops them rattling.

Guttering brackets - 3 per 6' run is what I think is right. You might be OK with 2. They're not that expensive, I prefer to use 3.

Fixing downpipe ears into brickwork - don't bother with pipe nails. Masonry bolts are much easier - the threaded type, like this.
http://www.screwfix.com/p/easyfix-concrete-bolts-10-x-80mm-10-pack/7513p
Not sure what would be best for fixing into stone - maybe pipe nails going into wooden wedges hammered into joints in the stone? Never tried it.

Putting it up - dangerous to do so off a ladder, get scaffolding or a tower! If you must do it off a ladder, at least as a minimum use 2 people and 2 ladders so you can hold the end of each section, it's heavy old stuff!

If you've got any downpipes with broken sockets, you can get "loose" sockets to replace them - don't throw the pipes away!

If you need any odd size or shape fittings then J & JW Longbottom Ltd have by far the biggest range - a proper old-fashioned foundry.

I think that's about it, hope that helps.

No reason to coat the inside of downpipes.

 

[BlueTed]

Thanks so much All!

 

[noj]

Of no real help to you but this is a great opportunity for the rest of us...

Do alternate sections with red oxide, zinc and maybe just hammerite direct to metal then report back in 10 years

 

[BlueTed]

Of no real help to you but this is a great opportunity for the rest of us...

Do alternate sections with red oxide, zinc and maybe just hammerite direct to metal then report back in 10 years

 

[MatthewC]

Of no real help to you but this is a great opportunity for the rest of us...

Do alternate sections with red oxide, zinc and maybe just hammerite direct to metal then report back in 10 years

If you do that then you can report back in about a year or two. My cast iron downpipes had a primer which I thought was OK but in fact it wasn't and the top coat flaked within a short time. Apparently it was "transport primer" which (I think) simply stopped it going rusty before they sold it.