Cleaning and Corrosion control Flashcards
what is used to clean transparent plastic windshields and windows of an aorcraft
mild soap and lots of Clean water
that is used to neutralize the electrolyte from a lead-acid battery that has been spilled on an aircraft structure
solution of bicarbonate of soda and water
what is used to neutralize the electrolyte from a nickel-cadmium batter that has been spilled on an aircraft structure
solution of boric acid and water, or vinegar
what solvent is recommended for removing grease from aircraft fabric prior to doping it
Methyl-ethyl-ketone (MEK) or lacquer thinner
what is the proper way to clean plastics
flush the plastic with clean water. Remove dirt by hand. plastics are easily scratched and usage or rags is not recommended
what causes corrosion
where is filiform corrosion most likely to occur on an aircraft
under a dense coating of topcoat enamel such as polyurethane. Filiform corrosion is caused by improperly cured primer
where is fretting corrosion most likely to occur on an aircarft
in a location where there is slight amount of relative movement between two components and no way for the corrosive residue to be removed as it forms
where is intergranular corrosion most likely to occur on an aircraft
along the grain boundaries of aluminum alloys that have been improperly heat-treated. Extruded aluminum alloy is susceptible to inter granular corrosion
where is stress corrosion most likely to occur on an aircraft
in an metal component that is continually under a tensile stress. The metal around holes on casting fitted with pressed in bushings is susceptible to stress corrosion
what areas of an aircraft are more most prone to corrosion
battery compartment, exhaust system and exhaust trails, wheel wells, lower areas of the belly (bilge), piano hinges, areas of dissimilar metal contact, welded areas inside of fuel tanks (especially integral tanks), metal fittings under high stress, lavatories, and food services areas
what is used to keep corrosion from forming on structural aluminum alloys
an oxide coating or aluminum cladding
how should an A&P minimize corrosion at piano hinges
piano hinges should be kept as clean and dry as practicable and lubricated with a low-viscosity moisture dispersing agent
how is the inside of structural steel tubing protected from corrosion
the tubing is filled with hot linseed oil and then drained
how does filiform corrosion usually appear on an aircraft structure
threadlike line of puffiness under a film of polyurethane or other dense finish system topcoats
what must be done to a piece of aluminum alloy to remove surface corrosion and to treat the metal to prevent further corrosion
remove the corrosion residue with a bristle brush or a nylon scrubber. Neutralize the surface with chromic acid or with some type of conversion coating. Protect the surface from further corrosion with a coat of paint
how may rust be removed from a highly stressed metal part
by glass blasting, by careful polishing with mild abrasive paper, or by using fine buffing compound on a cloth buffing wheel
what tools are proper for removing corrosion from aluminum alloy
Aluminum wool or aluminum wire brushes. severe corrosion can be removed with a rotary file
what type of device is used to remove surface corrosion from a piece of magnesium alloy
a stiff hog-bristle brush
what must be done to piece of aluminum alloy to remove surface corrosion and to treat the metal to prevent further corrosion
remove the corrosion residue with a bristle brush or a nylon scrubber. Neutralize the surface with chromic acid or type of conversion coating. Protect the surface from further corrosion with a coat of paint
how is rust removed from a highly stressed metal part
by glass bead blasting, by careful polishing with mild abrasive paper, or by using fine buffing compound on a cloth buffing wheel
what is corrosion preventive compound (CPC)
a waxy sealant or thin film dielectric that can be sprayed into aircraft structures to coat the surface and work its way between skins to prevent corrosion
what type of environment would CPC normally be used in
CPC are used in corrosive environments such as aerial agricultural spray operations and saltwater environment
how are CPC applied to aircraft structure
CPC are normally applied with high pressure spray equipment that creates a fog of the CPC material inside the aircraft structure. Long spray wands are used to reach difficult to access areas
what is used to clean to composite material prior to repair
acetone or methyl-ethyl-ketone(MEK) is commonly used. It is important to verify that the solvent residue is compatible with the resin system
where is dissimilar metal corrosion most likely to occur on an aircraft
anywhere different types of metal come in contact with each other, especially where moisture is present
what can be used to repair the anodized surface of an aluminum alloy
a chemical conversion coating such as alodine
what are three types of primer that may be used when painting an aircraft
zinc chromate primer, wash primer, and epoxy
what type of thinner is used with zinc chromate primer
Toluol or toluene
what type of primer is used when the maximum protection of the metal is required
epoxy primer
what are some different types of primer materials
wash primer, red iron oxide, gray enamel undercoat, urethane, epoxy, zinc chromate
how thick should a coat of wash primer be that is used on an aluminum alloy aircraft structure
it should be thing enough that it does not hide the surface of the metal
what are some different types of topcoat materials
dope, synthetic enamel, lacquers, polyurethane, urethane, acrylic urethanes
what is the primary structure purpose of a finish on a composite material
to protect the composite structure from ultraviolet degradation
what are the methods used to remove finishes from a composite material
by light sanding or abrasive blast with plastic materials
when mixing epoxy paint, should the converter be added to the resin or the resin to the converter
converter should always be added to the resin, never the resin to the converter
what should be done to a corroded aluminum alloy surface after the corrosion has been removed by mechanical methods
surface should be treated with a chemical conversion coating before the topcoats are applied
what may be done to the surface to prevent filiform corrosion beneath the topcoat
be sure that the primer is properly and completely cured
how it the finish removed form a fiberglass aircraft component that is being repaired
the finish must be sanded off. paint remover can soften the resin of which the component is made
how can a vinyl film decal be removed from an aluminum alloy surface
place a cloth saturated with cyclohexanone or MEK over the decal until it is softened, and scrape it off of the surface with a plastic scraper
why is retarder used in dope when the dope is being sprayed in humid conditions
the retarder slows the drying of the dope and keeps it from blushing
what is meant by dope blushing, and what causes it
Blushing is a a condition in a dope finished component in which moisture from the atmosphere condenses on the surface and causes some of the cellulose to precipitate from the finish. Blushing leaves a porous, dull, and weak finish
Blushing may be caused by the temperature being too low, the humidity being too high, or by drafts or sudden changes in the temp
what causes blushing in a dope finish
too high humidity
what causes fisheyes in the finish
localized surface contamination
where are the registration marks required marks required to be placed on a fixed-wing aircraft
on the vertical tail surface or on the side of the fuselage
what is the generally required dimensions of the registration numbers on the side of a fixed-wing aircraft
12 inched tall and 2/3 as wide as they are high. the letters M and W may be as wide as they are high. The humeral 1 and 1/6 wide as it is high
what is the regulation regarding the color of the registration marks
the color must contrast with he background and be legible
what is a cause of poor adhesion between the topcoat and the fill coats on a fabric surface
too much aluminum powder in the aluminum pigmented dope
what is a cause of rough finish on a freshly sprayed surface
too high automizing air pressure on the spray gun
what causes sags and runs on a surface that has just been sprayed
too much finishing material being applied on one coat
what causes orange peel, or spray mottle, in a finish
incorrect paint viscosity or improper setting of the spray gun
what cause pinholes in a finish
excessive atomizing air on the spray gun
what safety precaution must be observed when sweeping a paint room that has dried dope or lacquer overspray on the floor
the floor must be wet down with water before it is swept. static electricity from dry sweeping can cause a fire
what personal protection equipment (PPE) should be used while painting
respirator, eye protection, and skin protection
why are some portions of the structure of an aircraft dope proofed before they are covered with fabric
dope proofing keeps the fabric from sticking to the structure when the first coat of dope is applied. the fabric normally sags enough to touch the structure before it begins to pull that
what are some key application techniques for a quality paint job
correct spray pressure and spray gun setting, proper spray gun handling (even, overlapping spray patterns, spray gun distance) and good lighting
why should control surfaces be balanced after painting
weight and distribution of the paint may have changed, and the control surface may be out of tolerance
