Caulk for steel

Stan in Oly, WA

Well-known Member
I have been repairing and refurbishing the steel railings on the retaining walls on both sides of my driveway. The top horizontal member of the railing is made of a 1" wide, 1/2" high channel, open side up, with a 1-1/4" X 3/16" flat bar tacked on top of it. It's a nice design, but there's a problem with it. The intermittent tacking has allowed water to get into the channel creating enough rust to force the flat bar away from the channel in many places. It's difficult to repair because the top edges of the channel have become so thin that they burn through easily. I've got most of the parts tacked back in place and cleaned up, but without sealing the gap between the flat bar and the channel, the same thing is going to happen again. My neighbor offered me the use of his MIG welder to run a bead along the joints, but I think there's too much air movement to do it with shielding gas, and I suspect that flux core would burn through just as stick did. Anyway, I'd still have to grind it into shape, and there's about 80 feet of it. There must be a caulk that's suitable for steel. It will be primed and painted with oil based paint. If the caulk lasts as long as the paint, I'll be satisfied.

Stan
 
3M 8308 heavy-bodied seam sealer would be a good choice. auto body supply store or napa can get it.
 

I would also drill drain holes to the underside of the channel to allow drainage and airflow in future .
Sikkens make a good allround caulk that dries hard but retains a little flexibility so is suitable for steel .
 
I would agree, silicon, as long as its a type that will bond to steel, it should work well.
This is where a high performance material would work well. Dow 795. There is a distributor in Washington state, see below.

I would imagine readily available silicon sealant, like at H-D or similar should work, just check the product data on it.
Dow 795

Krayden
 
Urethane door and window sealer is paintable and very elastomeric. It sticks to all things (well maybe not the surface of a puddle) it is vary stable and the same basic material used to install auto glass windshields. Be sure it is "Urethane" Jim
 
If it were mine I would use a polyurethane caulk or sealant. It is very durable and elastic. It has very good adhesion properties and is paintable. Make sure the surface is clean before applying. The only real issue is with its tooling properties. I have found that if you run a bead and then wet your finger it will provide a nice appearance. It is not very forgiving or repeated tooling. In your situation you may not even need to tool the bead. Nephew who is a painter recommends it over other caulks. SikaFlex is one brand that can be purchased at Home Depot. Hope this helps.
 
3M 5200 Marine Sealant is an excellent urethane caulk that will stick just about anything to anything else. It is both sandable and paintable. You can find it in most marine hardware stores. I would expect that urethane sealers intended for auto body work would be similar. Sika also makes very good urethane sealants.

Do NOT use silicone. It doesn't adhere well to metal (compared to urethane caulks) and most silicone sealants are not paintable.
 
I used Sikkaflex from Home Depot after making a bunch of repairs to my sisters horse trailer. It's over in the concrete section, not in the paint section with the other caulk. Be sure to wear disposable gloves because it is the devil to get off your hands.

TM
 

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