rust - arrrg

[BurtEggley]

We all have fought it somewhere. I've been pretty successful in avoiding it many places, but one that has me stumped are two Kohler cast iron bathroom sinks. They rust under the chrome or plastic grommet that fills the overflow hole.

Bar Keepers friend has oxalic acid in it and gets rid of the rust that is there, but within a few days it is back. It gets really old having to clean it every three or four days. I am wondering if anyone has found something like say phosphoric acid etc., that can be painted all around and into the overflow hole then rinsed, that might keep it away for longer. Has to be safe on chrome, or stainless etc., what ever the grommets are made of. Last time it happened I replaced the sinks and it was gone for a year or two, but they are so expensive now going that route for a several year reprieve is not a viable solution. Having the countertops replaced and adding a different style sink is also not viable.

 

[Shiftless]

Try this Rustoleum product. Use this and then apply porcelain enamel touch up paint.

Rust reformer is a specialized chemical treatment that converts existing iron oxide (rust) into a stable, inert, and paintable surface. It eliminates the need to sand metal down to bare metal, chemically bonding with the corrosion to prevent it from spreading.

 

[rlitman]

I wouldn't bother with any sort of paint. You're never going to completely rustproof the inside of the overflow passage, and with paint, if there's ANY room for rust to start, you've lost the war.

I'd use a lanolin based corrosion inhibitor. Fluid Film would probably work ok, but it's a bit thin, so it can wash off, and the smell is offensive to many (Wool Wax is another similar and slightly thicker but even more smelly option). No-ox-id a-special is a cosmoline type grease (so lanolin based), that isn't smelly, and is often used to stave off corrosion inside steel water tanks, so it's much less likely to wash off than anything else I'm aware of. You could apply a film with a q-tip.

https://www.amazon.com/dp/B00HDF9EXE?tag=atomicindus08-20

 

[BurtEggley]

Thank you. Re the o-ox-id a-special, I have some already.

So maybe use some barkeepers friend that has oxalic acid in it to clean it then put some of the o-ox-id a-special on it.

Shiftless, thank you. I am thinking also about paint, and your suggestion. The rust inside the opening and under the grommets has to be 100% slowed or it will just come back. I have a classic car that had some rust so am well aware what is involved in the automotive world to stop it. In one small area which we could not easily get to or replace, we dug out as much of the rusted area as we could then treated it with a molten zinc sprayed to build it back up, and that stablized the area. But I do not see doing that to the sinks.

 

[toolmiser]

We also have about a 25 year old Kohler sink that is rusting around the drain and also the overflow.

 

[BurtEggley]

We also have about a 25 year old Kohler sink that is rusting around the drain and also the overflow.

I personally will never buy another Kohler sink or toilet. The new toto toilets we bought to replace Kohlers have been wonderful.

 

[rlitman]

I personally will never buy another Kohler sink or toilet. The new toto toilets we bought to replace Kohlers have been wonderful.

No comparison. But after growing up with these rust issues in cast iron sinks, I've always had vitreous porcelain sinks in my bathrooms and stainless sinks in my kitchens. The rust line coming down from the overflow is a nuisance, but when the rust creeps up from the drain and chunks of enamel start to fall off around the drain trim, it's game over. Porcelain is porcelain through and through, so corrosion never happens, though it can have it's own issues (mostly with flatness and fitup and being a bit less impact tolerant).

 

[dwasifar]

How about cold bluing?

 

[rlitman]

How about cold bluing?

It offers less corrosion resistance than the "browning" I'm suggesting. Which BTW means that acid cleaning to bare metal is not actually helpful. If you keep cleaning to bare metal, you'll continue to get "flash" rust, which washes off quickly and leaves a stain trail. You need to build up a brown patina for any oil to take a hold and give you continued protection.