Fixing a chip in a bathtub is typically a three-step process: cleaning the bathtub, filling the hole with epoxy paste, and then repainting the bath. Porcelain, fibreglass and metal bathtubs can all be repaired in this manner.
To fix a bathtub chip, we suggest using PC-11 56g White Epoxy Paste because it is waterproof, non-toxic, and once dry can be sanded down. By just mixing a small batch you should be able to cover a chip and lightly sand it down to make it blend in with the tub.
First wash the area with dishwashing soap and a green pad scrubber. This will clear the spot of oil, wax and soap residue. Your goal is to make sure that it is free and clear of loose chips and debris before you start putting on the epoxy paste.
No pre-sanding is required before using the epoxy paste as the surface you are working on is already rough. As soon as the surface is totally dry, you can begin the application of the epoxy paste.
I recommend not making the patch too high or proud of the surface of the tub. Try feathering the edges so that the patch blends in with its surroundings.
Once the epoxy has cured, you can sand it down starting at 240 grit and then using 320 grit or higher. If you've laid the patch evenly, only moderate sanding will be necessary to flatten the patch.
If you are lucky, once the epoxy has dried white it might match the bath and not require painting. But typically, you will need to paint the bathtub to mask the repair.
Remember that if you have chips in a bath that has been painted previously, all of the compromised paint needs to be removed before you can apply new paint. Prepare the surface by sanding the flaking areas with 120-grit sandpaper. Remember to wear a dust mask. Remove all the chipping paint and then sand back into the non-chipped area until you reach solid paint that is well bound. You can then swap to 240-grit sandpaper and smooth out any rough spots.