I think you should remove the sink and remove/treat the rust first. Then I would use clear caulk around the edges.

It looks like a neat sink! Can you pst a picture showing the whole thing?

Tough to think it is rust, more like just dirt/mold. Surely the sink was set with caulk under the rim. I would just toothbrush it clean with and then use some clear silicone caulk, smoothed so tightly that it doesn't show.

I'm curious too...what does that whole sink look like...most unusual.

-Babka

We also have a cast iron sink and before installing, the plumber sprayed the underside with some anti-rust stuff. Not sure what it was but he mentioned that sometimes those sinks rust from underneath and he wanted to be extra cautious to avoid that. Like Errant and Babka mentioned, he also applied some clear calk under the edges. Can you look under your sink to see if there is some more rust or maybe dirt/mold?

I have some of that too and it is definitely rust. In one area it seems there is a little gap in the caulk. I first noticed it on the front corner where you can see a little of the black edge. I'm really surprised Kohler does not treat this underside, at least around the edges, so it is not a problem. Having the sink removed to treat it is a big deal. I just had this installed and the plumber cost $300!

Use a credit card and dig out all the rust/contamination. Clean with acetone. Push 100% color matched silicone in the joint, spray it with Windex, spit on your finger, and wipe the excess. It's easy to gouge out and replace in a few years if you need to.

Thanks all so much for the responses. DH caulked when he installed it, but not around the edges.

Errant, we could remove the sink (easy for me to say, since I don't have to do the work!). annemouse - if we do remove it, we will spray with the anti-rust solution.

snookums2 - is this on your new sink? Yuck:(

Treb, I think I will start with your advice (like the idea of color matched silicone vs. clear, just as an extra precautionary step...). (PS - DH loved your idea of using Windex). Thanks!

You've probably seen this sink a hundred times at the big box stores. I've liked it otherwise. This was the vanity DH built; small bathroom, trying to maximize space. Note the small chip at left back (hopefully color matched caulk will hide a little) and how little space there is between the faucet/handles/sink and wall. (Definitely a cleaning challenge!).

{{gwi:2132865}}

Yes, it is a new sink. There is a tiny bit of rusting going on at the front corners, mostly seen on the papertowel when I wipe that area well. The other day I saw a little orange rust stain running out from the side towards the back - and I could poke the corner of the towel under, coming back with moisture. My plumber is pretty meticulous but seems a spot got a gap. The corners, you can see that black edge without enamel fully wrapping. I was worried about that before even noticing a bit of rust. I really think Kohler should have this base covered with a protective sealant coming out of the factory. Not needing a pre-install preventative procedure (which I was unaware of, until now).

He did use a 100% silicone clear caulk, very neatly done. I am going to call their CS.

Did that chip occur due to some rusting?

Gads, can we ever get something finished and just be done with it? No problems, nothing to worry about? This is supposed to last forever!

snookums2 - you're describing my problem exactly! This must be a fairly common problem for them.

The chip happened at some point between the time we unboxed the sink and finally installed it (so, our fault). I've asked Kohler about how to repair/color match that as well.

Thanks for posting the picture, oldbat! I had not seen that sink before, but I love the fun shape :)

You're welcome Errant! Following is Kohler's response, spot on with your suggestion. Looks like DH has some plumbing in his near future....

Thank you for contacting Kohler Co. I am very sorry to hear of the issue you are having with your sink. I will be happy to assist you.

The edge of the sink should have been sealed when it was originally installed. Since it has been rusting, I would recommend removing the sink, cleaning the edge of the sink with a rust remover, and then reinstalling the sink, making sure to seal the edge well using 100% silicone. From the photo, the sink does appear to be biscuit in color, but it is difficult to say for certain from photos.

We do not have a brand of sealant that we offer or recommend to color match the sink. A quality sealant that in biscuit in color or clear is typically recommended or the best results.

If there is a chip in the sink, we offer an enamel touch up paint that can be used. This is part 500306, and can be found at the following link:

500306

So when they say sealant, they just mean caulk? That doesn't solve the problem of the enamel stopping short of the underside, leaving that little black line. I read a thread going back to 2002 that they stopped using a spray gun to catch that edge and problems began with rusting.