Salt deposits on brick are a sign that moisture has regularly passed through it. As the water is drawn into the masonry and evaporates, it leaves behind its salts on the surface. This white residue is called efflorescence. Efflorescence itself is not a concern, but the regular penetration of moisture into the wall system can cause damage internally. The removal of efflorescence is done with chemicals specially designed for this task. These products are acid-based, so take the appropriate precautions.
Wet the brick with water. If the surface you're trying to repair is outdoors -- an exterior brick wall, for example -- use a hose.
Put on your safety glasses and acid-resistant gloves to protect yourself.
Mix the efflorescence chemical solution with water in a bucket according to the manufacturer's directions on the back of the bottle.
Dip the scrub brush in the solution and apply to the salt stain.
Move the brush back and forth in different directions until the stain has been removed. You may need to use several applications of the chemical solution to fully remove the salt.
Wash the chemical cleaning solution off the brick with water.
Test the cleaning solution on an inconspicuous area of the brick to assure it doesn't damage the appearance.
In the event that you get the cleaning solution on yourself, quickly apply baking soda to neutralise the acid.