Enamel kitchen sinks become accidently chipped from dropping dishes or pots and pans on them. When this damage occurs, the only remedy is to repair the porcelain on the sink before the metal underneath it starts to rust. Repairing a damaged enamel chip is relatively easy and can be accomplished with a two-component epoxy made up of a catalyst and hardener. This epoxy is found at most hardware stores and comes in a variety of colours.
Wash and dry your sink thoroughly. Make sure you rinse it well enough to remove all the cleaner.
Sand the chipped area to remove any rust and to rough the area up a little. Confine your sanding to the chipped area, so you do not scratch the rest of the sink.
Pour some rubbing alcohol onto a rag, and clean the area that you sanded. Be sure to let the area dry thoroughly.
Mix the epoxy compound together on a piece of smooth scrap tile or glass, adding any colour slowly until the repair compound matches the sink.
Apply the compound with the razor overlapping the chipped area slightly. Scrape off any extra epoxy until it is flush with the sink surface.
After the repair patch dries slightly, use a cotton swab dipped in nail polish remover to blend the edges of the compound into the surrounding porcelain.
Let the repair patch dry thoroughly for about 24 hours or for the time specified on the two-component epoxy packaging.
You might need a couple of colours of epoxy to match the correct colour of your sink. Even if your sink is white, because many different shades of white exist, mixing multiple colours can better match the shade than just one.
Be careful with the razor blade and any flakes of porcelain you scrape off the sink. Both are very sharp.