I have an old railing on one of the windows of my apartment (floor to ceiling window). The top face of bottom rail of the railing is quite rusted between a few of the vertical slats. I scraped off the loose rust and treated it with rust reformer. Problem is that the surface is now slightly concave, since it rusted in the middle more than the edges. It would actually hold water in the concave area, which I'm afraid will lead to more rust soon.

Can I ...
(a) paint the rusty areas with a zinc-bearing primer after the rust reformer (the kind with tannic acid) dries?
(b) build up the concave area with a metal-bearing epoxy
(c) paint over the whole shebang with a topcoat

Any better solutions or advice? Replacement of the railing is not an easy option at this point.

Thanks!

Well you could clean it down and use waterproof fiberglass auto body filler. Then level it and paint it.

The waterproof filler is usually called short hair fiberglass. Unlike body filler it is waterproof. I would not use normal body filler.

I would use some form of epoxy.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Agree the epoxy might be better. Depending on quantity required as epoxy based products are not cheap. Short hair fiberglass auto body filler bonds well too. I am thinking about probably cost in the USA. Maybe 14.00 a quart.

This is what I've used in similar circumstances: Amazing Goop 4-oz. Super Mend Epoxy Paste Kit (8-Pack)-5330031 at The Home Depot

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

^^^

Did you apply it over "bare" metal, or did you prime before applying it? The area to cover isn't large -- probably a few of the duplex vials of epoxy would suffice.

I've used it to patch lead and cast iron sewer pipes in addition to using it to fill cracks in exterior wooden window sills before painting. I just sanded the metal with sandpaper and put it on. Still holding 15 yrs later.

You can buy the stuff in a variety of different sized containers in lots of hardware stores. It's easy to mix since the ratio is 1:1.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

How does it compare to JB Weld?
Being a paste, it's probably thicker when applied?

JB is one of my favorites.

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

Not that familiar with JB Weld. It's kind of like a thin peanut butter.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

You can also get epoxy putties - like KBS numetal

NuMetal - Epoxy Putty - Body Filler - KBS Coatings

Other similar products are available! ave a look on Eastwoods for example...

Always treat the surface for rust before applying any filler.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I would use epoxy, polyester is not water resistant and requires a very good top coat.
You can use epoxy filler (ready to use) or mix it yourself.

I use the ready made filler only for small repairs, for larger repairs it is much cheaper to use resin, harder and glass pearls to make it in a "putty" form.

Unlike premixed polyester, epoxy needs very precise measurement of the amounts to be mixed, except for the glass pearls, just add until you have the right consistency.

Be careful with the glass pearls, they are very light, always wear a mask!

Rob

Thanks, all -- I think I'll go with the epoxy (without filler) when it dries out and is warm enough to use it.