The RSJs holding up my upper storey have been exposed as part of building work. They have slight surface rust (I'd say powdery 0.5mm after 70 years) (web is 10mm thick) Not really going to affect load bearing capacity, but it may be work painting them with something. Hopefully wont need to clean them to fresh steel - that would be a horrid job. What should I slap on them to stabilize the surface ? Cheers, Simon.
I've used Hammerite No1 Rust Beater on a couple of cars and not bothered with any further coats - though is both a primer and undercoat - and it has remained in excellent condition, with no further rusting. I wouldn't hesitate to use it in your situation, as it can be applied directly to rusty metal.
Andy C
Many rust removers are simply acids. This stuff converts rust into an inert black layer
I've used Kurust (another Hammerite product) to good effect. Converts the rust to phosphates I think. Certainly stopped rust on bits of car and on rusting corner reinforcement in plaster. The last bits on a car have not been painted over and have stopped rusting.
Just use red oxide primer like the steel suppliers do.
In message , The Medway Handyman writes
bought it from at a better price than that quoted. My local friendly small garage recommended it. I've painted it on, but it's too early to say about results.
I don't have any of the product but...AFAIK... The active ingredient of the paint formerly used for rust protection of steel was lead oxide and because the oxide of lead is red in colour the product was called red oxide paint. You would know a tin of real lead oxide paint because it is extreemly heavy compared to a similar sized tin of ordinary paint. However I think the sale of real lead oxide paint has been banned for many years because of the toxicity of lead oxide.
The safety data sheet on the product you listed doesn't mention lead at all, so i take it there is no lead oxide in it, and the word lead doesn't appear in the phrase 'Red Oxide Primer'.
Perhaps someone knows what the active rust protecting ingredient is?
Roger R
Trimite Red Lead - now that takes me back a few years. It was used in a BS standard for measuring the surface area of odd shaped articles. Weigh the article dry (having been heated to 105C IIRC, dunk in the paint, allow to drain and dry and then re-weigh. Then calculate the surface area based upon the paint taken up.
I've still got some of the samples I dunked in 1974/5 in a bedroom upstairs. Now I'm in a morose state. No wonder my children are stupid. What should I do with these samples? Can I legally dispose of them. Have I committed a crime retaining these samples? Answers, please!
Seriously, in answer to the OP, is there a need to paint the RSJ? If it will not feature in the habitable space and will be in a dry concealed location, why paint it?
If after 50yrs+ there is just a dusting of rust, forget about it...
- Black rust is millscale and actually inhibits further rusting
- Paints like hammerite can trap moisture if cracked (unlikely on an RSJ)
- POR is good, but forget welding to it, or mag-drill n bolt to it either
- Rust converters work, but only to a very limited depth
- Red Oxide does not have lead, probably some other oxide
Typically if you want to protect structural steel you...
- a) 3M Clean-n-Strip disc to a shiny surface including pits
- b) media blast to a "sa2" bright shiny surface including pits
- Paint with zinc epoxy primer =A350 or epoxy mastic =A330
To touch up coated steel, use galvafroid...
- Real cold zinc primer, =A315 for 250ml, extremely heavy
- Only works where zinc can directly contact steel not rust
- No abrasion resistance, but very effective
I'd rather put the money towards replacing guttering early, because that can really leave a trail of problems.
Well I'll probably just leave it then. I'll just hoover up the small amount of loose dust on the flanges. I've just replaced the guttering as it happens ... ;-) Simon.
Well done, avoids you finding all those outer-to-inner-leaf water paths! :-)
Anyone doing guttering on an old house:
- Check the felt into the guttering, it is often rotted
- So slip DPC under the bottom row of tiles carefully
That can stop wind blown water migrating toward rafters, soffits, bedroom ceilings, wallplate, cavity.
Something to remember if you ever get a tower up for other jobs, saves about 1k. Almost worth buying a tower for (assuming you can handle heights which I can't... well I can... it's just I impersonate an incontinent seagull the higher I go). "You have some big birds in this area"... "that is not the birds".
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