Covering rust stains

[Tom]

As ever two steps forward, one step back. Before the decorators started I coated all our exposed steelwork (already red oxide primed) with two coats of satin hammerite (oil based, 8yrs guarantee). The decorators have gone over everything in emulsion and quite a few rust stains have leatched through, which is annoying. Would another dab of hammerite on these work as an adequate stain block or should I try something else?

The main contractor covering the internal works have suggested "rust-oleum or similar", but I need to get this right.

Thanks all

[Conor]

Is this internal steel? Is it not being boxed in then? What about fire protection?

 

Anyway, sand back the offending areas back to the steel, re prime and paint again.

[markc]

Hammerite on top of red oxide is pretty pointless and emulsion definitely won’t key to hammerite and will peel off. Scrape off whatever you can (you may find the hammerite comes off as a layer to make things really easy) rub down and rust and seal off with zinzer BIN or similar before the emulsion.

[Tom]

1 hour ago, Conor said:

Is this internal steel? Is it not being boxed in then? What about fire protection

Yep, internal. Not being boxed in and doesn't need protection.

 

56 minutes ago, markc said:

Hammerite on top of red oxide is pretty pointless and emulsion definitely won’t key to hammerite and will peel off.

There were a few rust spots coming through the red oxide so I gave a spray of dinotrol where it was obvious, then two coats of Hammerite over everything. My intention was this would be the finished colour, but the decorators, in their wisdom, have decided to just spray everything with emulsion, which has now caused some rust dicolouration to bleed through. Would have been fine if they'd left it as-is.

 

Don't fancy having to rub it all back as there are a lot of steels and a lot of areas where these spots have come through. Kind of think it's the decorators responsibility to sort TBH! What think you?

[Nick Laslett]

I know very little about this topic. But after a buildings control visit, we had to re-paint 2 of our steel beams. There is an NHBC note on this topic. 
 

https://nhbc-standards.co.uk/6-superstructure-excluding-roofs/6-5-steelwork/6-5-3-steel-grade-and-coatings/

 

Specifically Table 5 on this page. 
 

 

There are obviously a lot of paint coating options for steel and many differing opinions. Farmers forums seem to be especially animated by this topic, also classic car restorers. 😉
 

I just keyed in the phrase “zinc phosphate epoxy primer”, which led me to this product Johnstone's Quick Dry Zinc Phosphate Primer Red Oxide. Reassuring expensive ☹️.

https://www.brewers.co.uk/product/AF12502310J

 

I then bought a poly disc from EBay to strip the rust and old paint using my angle grinder. Very messy approach, I would not recommend, but I had to do a 5 metre long beam. 
 

 

They come in 3 different colours, which indicates strength of abrasion. 
 

https://www.amazon.co.uk/Polishing-Effective-Remover-Abrasive-Grinder/dp/B08YZ286F5

 

 

 

Edited November 25, 2023 by Nick Laslett

[markc]

@Tom yes I see now, the hammerite was to be the decorative, not protective finish. The staining through the emulsion is more likely to be oils from the hammerite rather than rust.

[Tom]

1 minute ago, markc said:

The staining through the emulsion is more likely to be oils from the hammerite rather than rust.

Definitely rust leaching through, I'll get a pic if I can.

 

Thanks for all that info @Nick Laslett, however these are internal steels in a heated environment, so classed as C1 I think.

[Tom]

What might be more of an issue though is the emulsion flaking off the hammerite later. I am paying a lot for the decoration and seems like this is a major mistake

[joe90]

1 hour ago, Tom said:

seems like this is a major mistake

By the decorators?, did you specify what was to be painted? , if so I believe it’s their responsibility to put their mistake right.

[Nick Laslett]

1 hour ago, Tom said:

Definitely rust leaching through, I'll get a pic if I can.

 

Thanks for all that info @Nick Laslett, however these are internal steels in a heated environment, so classed as C1 I think.

 

Hi @Tom, I completely agree that your steels are now in a C1 environment. My steels developed their rust during the period they were in a C2 environment.

[Tom]

A few pics...

[Tom]

4 hours ago, joe90 said:

By the decorators?, did you specify what was to be painted? , if so I believe it’s their responsibility to put their mistake right.

I didn't ask the decorators to spray the steels with emulsion as I fully intended the hammerite to be the final finish. I specifically went for the satin Hammerite because of this.

[joe90]

15 minutes ago, Tom said:

I didn't ask the decorators to spray the steels with emulsion as I fully intended the hammerite to be the final finish.

BUT, did you tell them that???, they may not have understood but if you did tell them then rectification is their problem.

[Tom]

I didn't explicitly say not to paint the steels as assumed no one would paint steels in emulsion. I was clearly wrong.

The situation remains that I need to rectify it and there is over 50m of steel!

Would a coat of zinsser suffice or would it all peel off eventually if there is emulsion on the hammerite?

[Gus Potter]

15 hours ago, Tom said:

As ever two steps forward, one step back. Before the decorators started I coated all our exposed steelwork

Is it old steel say in an old barn or new steel?

 

In your last photo I think I can see some roughness on the outside edges of the bottom flange suggesting it is old steel. If so you'll need to take that back to the bare metal. Do it now as later it will be messy job and spoil your curtains for example. Rust dust is a bugger as it stains many things it lands on.

 

If new steel then the SA2.5 blasting should have removed the mill scale.

 

 

[Tom]

New steel, but a few rust spots coming through the red oxide in places, hence why I rubbed it back gave a spray of Dinitrol and two coats of Hammerite. It would have been fine had the decorators not covered in emulsion. Any tiny spots that would have been invisible are now visible due to leaching out into the emulsion.