Technical Standard 631 Coatings Evaluation and Maintenance Flashcards
Preparation of Ungalvanized Steel. Metallic surfaces other than aluminum and galvanized steel are best cleaned by?
- dry blasting methods.
- Water jetting may be used to prepare un-galvanized steel surfaces.
Preparation of Galvanized Steel.
-Avoid heavy blast cleaning of galvanized steel
-Chipping hammers shall not be used on galvanized surfaces
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Preparation of Aluminum.
-Do not use steel shot, steel grit, copper slag, or any coal/boiler slag abrasives such as Black Beauty that contain iron or copper because they can contaminate
the aluminum surface.
- Use garnet or aluminum oxide blasting material/abrasive paper with no metallic content.
Epoxy. Epoxy vehicles are made up of two components that are premixed before use:
an epoxy resin and a polyamide hardener.
-Anything left at the end of the day must be discarded.
-Epoxy paints tend to chalk on exterior exposure so that low gloss levels and fading can be anticipated; otherwise, their durability is excellent.
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Oil.- Linseed oil is the major vehicle in oil house paints. These paints are the oldest type of coatings in use and have the longest history of performance.
They are
recommended for hand cleaned iron and steel. Oil paints are not particularly hard or resistant to
abrasion, chemicals, or strong solvents, but are durable in normal environments.
Polyurethane Restrictions.
Two-part polyurethane coatings that contain isocyanate compounds pose a serious health threat and are therefore prohibited except as required to
maintain aircraft or other specific items required elsewhere in this guidance such as aids to
navigation.
-The alkyd modified polyurethanes are thinned with mineral spirits paint thinner and do not list isocyanate
as a hazard on the MSDS/SDS.
Boxing.
Boxing is a mixing procedure where a material is repeatedly poured back
and forth between two containers.
Brush Components. The component parts of a brush are generally as follows:
- The handle is made of hardwood or plastic and is shaped to fit the hand for the specific type of work the brush is designed to perform.
- The setting of the handle holds the bristles in the proper formation.
- The ferrule, which is the connecting link between the handle and the stock (bristles), must be correctly and sturdily constructed so the handle and the stock will not come apart. Ferrules are generally made of steel, nickel, tinplate, or aluminum.
- The stock is the working part of the brush and generally contains natural or synthetic bristles.
The wrist and arm motions should be free, easy, and not forced. Hold the brush firmly with fingers.
In holding the brush, the fingers should not go beyond the metal ferrule onto the bristles.
When painting, dip only .
-half the bristles into the paint
-Hold the brush at right angles to the surface being painted with the end of the brush
just touching the surface.
Roller Cover Materials.
- The standard size cover (for standard rollers) has a 1-1/2 in. inside diameter.
- “Nap” is the thickness of the cover and generally a thin nap is used on smooth surfaces
- thick nap is used on rough surfaces
Mohair
This type cover is recommended for applying enamels to smooth surfaces.
Chalking. Chalking is the result of weathering of the paint at the surface of the coating.
-The vehicle is broken down by sunlight and other destructive influences, leaving loose, powdery
pigment at the surface that can easily be rubbed off with the fingers
Checking is described as tiny breaks that take place only in the upper
coat or coats of the paint film without penetrating to the substrate.
Cracking describes larger and longer breaks that extend through to the substrate. Both are a result of stresses in the paint film which exceed the strength of the coating.
Alligatoring.
Alligatoring of a paint film, when the outer layer of paint cracks and presents a pattern similar to alligator leather, occurs when relatively hard finishing coats are applied over relatively soft priming or underlying coats
