問題一覧
1
What causes dope to blush?
1. “High humidity” causes the dope to blush 2. drafts over freshly dopped area 3. Low temperature
2
How do you correct dope blushing?
wait until humidity improves, apply another cote of dope 1. A retarder may be used in place of the thinner (amount depends on humidity) slows evaporation 2. Reduces the tendency to blush 3. All blushed dope must be sanded off and the area needs to be re-sprayed
3
What is orange peel?
An irregularity in the surface resulting from the inability of the “WET FILM” to level out
4
How is orange peel caused?
Causes: 1. Caused by improper spray technique 2. Improper adjustment of the spray gun 3. Use of thinners that evaporate too fast 4. Not enough reducer (too thick) 5. a draft over the surface of freshly sprayed dope 5. Too little flash time between coats 6. When the ambient or substance temperature is either too hot or too cold
5
How do you prevent orange peel?
1. remove the film and start over 2. Light orange peel can be wet sanded or buffed out with polishing compound 3. Extreme cases must be sanded smooth and re-sprayed
6
What do sanding scratches look like?
1. Appears in the finish paint when the surface has NOT been properly sanded and or sprayed with the finish coats 2. Ususally shows up in non-metal surfaces 3. Scratches may also appear if an overly rapid quick-drying thinner is used
7
What can you do to REPAIR sanding scratches in a paint job?
1. Only fix AFTER the finish coat has set up, sand down using a FINER grade of sand paper, 2. follow that with a recommended sealer, then re-paint”
8
What causes sags and runs while Painting?
1. “ Caused by inadequate surface finish” 2. Also caused by too much dope being applied to the surface at one time 3. Dope being too THICK (too much reducer) 4. Ensure the surface is clean apply dope sparingly and ensure it is properly thinned out
9
List the factors that cause poor paint adhesion?
1. Improper cleaning of the surface to be finished 2. Application of the wrong primer 3. Incompatibility of the top coat with the primer /selection of the wrong grade reducer 4. Improper mixing of materials
10
What is dope roping?
“Condition of aircraft dope being brushed onto a surface that causes the dope to form a stringy uneven surface”
11
What causes dope roping?
Dope being too cold or improperly thinned
12
How to prevent dope roping?
1. Use a bit more thinner 2. Allow dope to warm up to room temperature
13
Why are piano-type hinges so susceptible to corrosion cause and prevention ?
dissimilar metals
14
How should corrosion be removed in stressed steels?
very carefully, don’t want to overheat
15
After you finish welding a fuselage or engine mount and before priming, what should you do next?
Put linseed oil
16
What is an inexpensive quick way to check a metal tube for corrosion?
Probe the tubes with a prick punch
17
Why are water displacing CICs sprayed on?
to displace water?
18
Why are CICs used
prevent corrosion
19
How long should you wait to apply primer on recently prepped steel parts?
Maximum of 1 hour, should be done right away
20
What causes fisheyes?
Oil greases
21
What is the most common method of Galvanizing?
hot dip
22
What is chrome plating?
“Often referred to as chrome Technique of electroplating a thin layer of chromium onto metal or plastic” Provides; 1. Provides corrosion resistance 2. Eases cleaning procedures 3. Increases surface hardness
23
What is nickel plating?
“Is a technique of electroplating a thin layer of nickel”, Provides; 1. Corrosion resistance 2. Wear resistance 3. used to build up worn or undersized parts 4. can be decorative
24
What is galvanizing?
applying zinc coating to steel or iron to prevent rusting
25
How are pinholes caused?
temperature of dope room is too high
26
Most familiar type of corrosion is?
ferrous oxide (rust)