Rust Doctor is a very versatile product. Here are various ways you can use Rust Doctor to treat and seal rusted metal:
Spraying Rust Doctor in hard-to-reach areas: One of the most difficult problems in treating rust is access to the rusted area. In car restoration, for example, the inside of doors is often a difficult area to to treat; seams and welds often contain rust. One solution is to use a spray bottle to squirt Rust Doctor into hard to get at places. By setting the spray adjustment to a stream, you can direct Rust Doctor at the elusive welds and seams. Follow-up by using a spray gun to spray the remainder of the inside of the door to completely stop any rust that is present and seal the metal.
A syringe for tight quarters: Another method for getting at difficult places is to use a syringe to squirt Rust Doctor into tight locations where you need more control than the spray bottle provides. The syringe will shoot a stream of Rust Doctor into those hard-to-reach places. You can easily control the force and quantity of the spray by varying how hard you push on the plunger.
Large surface areas: To clean large areas of rusty metal, pressure washing will effectively remove dirt, rust, grease and loose paint in one operation. For storage tanks, car frames and bodies, metal structures and etc., high pressure washing will effectively prepare the surface for Rust Doctor treatment. If grease is present, add a degreaser such as Grease Doctor to the wash water.
Removing grease: Before you treat metal with Rust Doctor, you must remove any grease or oil that might be present on the rusted surface. On very old metal, oil down in the rust is difficult to see. One way to check for oil or grease in the rust is to spray the surface with a fine mist of water. If oil is present, the mist will lay on the surface. Without the presence of oil in the rust, the mist will soak into the rust, indicating that you will not need to worry about a degreasing solution or cleaner. Try several areas to be sure oil or grease in not present.
Protecting from overspray: When spraying Rust Doctor on frames or large surfaces, it is helpful to cover nuts on bolts that you may need to remove in the future. Because Rust Doctor converts rust to magnetite, rust on the end of a bolt will become very hard magnetite. This hard surface will make it more difficult to remove the nut. Put tape over the end of the bolt and nut so the Rust Doctor does not convert the rust to magnetite. When you want to remove the nut from the bolt, you can use a rusted nut releasing product on the rusty nut and bolt.
Welds and rust: When treating metal with Rust Doctor, it is important to force Rust Doctor into places where metal is welded or riveted. Rust builds up where the two pieces of metal are attached. Foam brushes work very effectively at forcing the paint between the metal pieces. Even if you can't force Rust Doctor completely between the metal, it will create a barrier along the outside edges to keep moisture and oxygen from reaching whatever rust could not be treated. This is important because the rust will continue to grow if it is not sealed off. If the surface is painted, rust stains will appear along the edges of the seam where the metal is connected if that connection is not sealed off.
Special treatment for car body panels: On automobile bodies, it is important to treat the front and back of metal body panels. If you only treat the front of a panel and then paint it, rust will migrate around the edges from the backside of the panel and stain the paint or create bubbles that eventually cause the paint to release. In some cases additional panels cover the backside of body panels, making it difficult to treat rust. It may be necessary to drill holes in these covering panels (this is inside the body and not visible) and spray Rust Doctor between the panels to stop the rust. This is the only way this rust can be stopped. The holes can then be welded or filled with rubber plugs.