I've got a Medium-density fibreboard (MDF) sink cabinet that is at least 30, if not 50 years old. The bottom has gotten wet a few hundred times from a shower that was near it, and it is flaking apart at the bottom where it meets the linoleum. It's also right by the laundry shoot, so it gets rubbed on a lot. I'd like to patch it with something water resistant, then paint and sand the whole cabinet smooth.
What should I use for patching it? Is there something more water resistant than wood putty? It should be fine if a soaking wet towel gets thrown next to it and sits for 3-4 hours a dozen times. I will yell at the kids, but I'm sure it's going to happen.
NOTE: I will probably sand off most if not all of the paint, so a thin coat of whatever on the paint or the MDF should be fine.
Best Answer
You probably want an epoxy based filler such as Bondo. A variety of manufacturers have a version of this.
These products are a little more complicated to use than traditional wood fillers, but they are pretty impervious to moisture once they harden. You need to mix small batches that can be used in a few minutes. Nitrile/latex gloves are a must.
Once done, better than wood or MDF for durablility.