The metal in faucets and sinks is exposed to humidity and air every day, and this triggers a chemical reaction which eats into the steel. Along with this chemical corrosion, the vitamins in the water may build up on the tap, leaving corrosive deposits. The layers of rust and buildup form bonds that join pieces of the tap together, which makes it difficult to remove maintaining nuts, water-line connections or even to turn the tap handle. To loosen the pieces and restore their usefulness, break the bonds caused by the corrosion.
Turn off the water supply to the sink. If you’re able to turn the tap on, then do so, and let the water from the pipes drain out.
Scrape away as much of the corrosion from the tap joints as possible using a wire brush. Occasionally just removing some of the buildup can free the joints. Try to turn the trapped part with a wrench.
Heat the corroded part of the faucet using a hairdryer in case it won’t turn. The metal swells as it heats up, and this may loosen or break the bond caused by the corrosion. Again, attempt to turn the part with the wrench.
Let the metal cool off if the part is still stuck. When it is cool to the touch, squirt a penetrating oil into the corroded joint. Let the oil function for so long as necessary. Apply more oil every few hours if the part doesn’t loosen quickly. Scrape off pieces of corrosion using the wire brush as they come loose.
Harness the trapped part gently with a hammer if necessary to aid the oil function. If the part is small or delicate, position a middle punch against it and tap the middle punch using the hammer instead of the tap itself. The force of the hammer along with the oil should be sufficient to break the bond of the corrosion and loosen the tap.