List at least four sources of corrosion hot spots and cite how they can be avoided

Question

What will be an ideal response?

Answer 1

• It may be an area of a seam, welded area, or any area where repairs have been made or the metal has become exposed by one or more of the following ways.
• During the repair process many tasks are performed that could result in hot spots developing. Whenever heat is applied such as in cutting and welding operations, the metal surface is exposed and left somewhat compromised for a corrosion hot spot to form
• Many times welded pulling studs or a non-consumable heat attached puller is used for repairing the metal. A considerable amount of heat is required to attach them and any surface coatings on the back side of these areas are burned away or form blisters on the surface.
• Drilling holes is often required to temporarily hold the replacement panel during installation and occasionally to attach the trim back onto the vehicle. In addition to the exposed edges of the holes becoming a potential hot spot, the shavings that are created from the drilling operation often fall into crevices and seams at the bottom of the panel being drilled. Rarely are these shavings removed, thus leaving another spot for rust to start forming. Bare or uncoated steel left lying against even a coated surface is an open invitation for oxidation to eventually occur.
• Hammering to stress relieve while pulling and repairing the metal may also cause the corrosion protection and surface coatings to become cracked and compromised.
• The use of spoons, pry picks, and other hand tools invariably scratches the paint and protective coatings. Therefore, any area that is part of the repair procedure must be addressed prior to returning the vehicle to the owner.
2. List four steps in sequence that must be followed when corrosion protection must be put into place on a bare steel surface that hasn’t been previously coated.
ANS:
• Wash with soap and water to remove the water soluble contaminants from the surface.
• Wipe with a wax and grease remover to remove any petroleum base contaminants from the surface
• Abrade the bare surface with an abrasive ranging from 80 to 120 grade

• Saturate the bare surface with a phosphoric base metal conditioning material. This is the equivalent of the phosphate treatment used by the manufacturer and should be applied liberally and the solution must be allowed to dwell on the surface for at least one minute, scrubbing it with a plastic scouring pad. While the material is still wet it may be necessary to rinse it off with water, wipe it dry or simply let it air dry, depending on the manufacturer's recommended procedures.
• Apply a primer coating