T.O. 33B-1-13-21softer though still somewhat abrasive. On highly polished surfaces, residual powder from the bath can contribute torapid corrosion.3.2.5.1.2 Vehicle.The wet method inspection process will normally leave the carrier liquid or vehicle on the test surface. If the vehicle isoil, it can be removed by vapor degreasing or solvent cleaning. If the vehicle is water, the residue will consist ofwetting agents and water soluble corrosion inhibitors, which may be removed with a plain water rinse or spray.Regardless of the type of vehicle used, the part should be cleaned as soon as possible after inspection anddemagnetization.3.2.5.2 Methods.CAUTIONPost-cleaning methods that use water can cause corrosion of the test surfaces if thewater is not promptly removed. Thoroughly dry off the surfaces by wiping, heatingor blowing off with properly regulated compressed air.Regardless of whether the wet or dry visible or fluorescent magnetic particle inspection process is used, once the carrierliquid or vehicle is removed, the requirement for removal of the magnetic particles is the same. Thoroughlydemagnetize the part, and then remove the magnetic particles by wiping or scrubbing. Cleaners or detergents cannotbreak the magnetic attraction. The particles cannot be dissolved from the surface, as they are a ferrous oxide.Mechanical scrubbing or detergent washing may be necessary. Solvents may be used to remove the residue, and insome cases the use of ultrasonic cleaning has been successful.3.2.5.3 RequirementsFollowingPostInspectionCleaning.After inspection by the wet method using a petroleum distillate as the bath liquid, the surfaces of parts are leftvulnerable to corrosion. The bath vehicle is, by specification, free of any residual non-volatile material, and when itdries it leaves no protective film. Every effort shall be taken to clean a part and apply a protective finish as soon aspossible after the inspection. When water is the vehicle of the bath, the dried film on the surface of a part consists ofthe various conditioners that have been used in the bath formulation in addition to the residual magnetic particles. Oneof the conditioners is a corrosion inhibitor, so that some corrosion protection is afforded by this inhibitor after testing.However, this is by no means permanent and a protective finish should be applied as soon as possible.3.2.5.3.1In the event a functional material, such as oil, grease or anti-seize compound, is removed from the part to facilitateinspection, the same material shall be reapplied after the part has been inspected.3.2.6 DisassemblyRequirements.3.2.6.1 Requirements.It is usually preferable to disassemble parts before inspection for the following reasons:a. Disassembly makes all surfaces and areas accessible.b. Boundaries between two magnetic pieces, or between a magnetic and a non-magnetic piece, will createa leakage field that may confuse inspection.c. It is usually easier to handle disassembled parts.
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