Section 3 - General Process
MCP - Metal Coating Process, LLC
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1. What should the sulfur content limitation be for 300-series stainless steel to be electropolished?
a) 0.005 %
b) 0.003 %
c) 0.050 %
d) 0.030 %
2. What is the best choice of sheet metal finish designation for electropolishing of the material?
a) No. 6
b) No. 8
c) No. 2 D
d) No. 2 B
3. Is buffing recommended prior to EP?
a) Yes
b. No
4. Describe the Bielby Layer.
a) Metal is oxidized.
b) Metal is smeared.
c) Metal has solution residue.
d) Anodic film.
5. How many amps can a piece of copper carry if the copper is 3/8” x 1”?
a) 725A
b) 500A
c) 375A
d) 600A
6. What is the effect of loose rack contacts on the finish?
a) Burn marks
b) Gas streaks
c) White residue
d) None of the above.
7. What is the effect of oxygen gas bubbles if not controlled?
a) Explosion
b) Damage to cathodes
c) Pitting
d) Streak marks on part of the surface
8. What will likely happen to the end parts on a rack of several parts?
a) Parts will be elongated
b) Nothing
c) Excessive metal will be removed
d) Parts will be dull
9. Name the recommended wet process steps in proper sequence.
a) Alkaline Clean> Rinse>Nitric> Rinse>EP>Rinse
b) Alkaline Clean>Rinse>EP>Rinse
c) Alkaline Clean>Rinse>Deox>Rinse>EP>Drag Out>CFR>Nitric>Rinse>Hot Rinse
d) Alkaline Clean>Rinse>Deox>Rinse>EP>Nitric>CFR>Hot Rinse
10. Name the recommended steps in pre-treatment.
a) Alkaline Clean>Rinse>Deox>Rinse
b) Alkaline Clean>Deox>Rinse>Rinse
c) Deox>Rinse>Alkaline Clean>Rinse
d) Alkaline Clean>Rinse>EP>Rinse
11. Why is an alkaline cleaner recommended?
a) To remove weld scale
b) To remove EP solution residue
c) To remove heat tint
d) To remove oil and grease
12. What problems can occur as a result of inadequate cleaning?
a) Smooth, bright finish
b) Non-uniform finish
c) Overheating of bath
d) Increase in S.G.
13. Name three things the acid bath can be used for in the pre-treatment process.
a) Remove weld scale, remove heat tint, remove anodic film.
b) Remove nitric acid, remove alkaline, remove nitrogen.
c) Remove anodic film, remove gas streaks, remove EP residue
d) Remove heat tint discoloration, remove weld scale, neutralize alkaline carryover.
14. What chemical is suitable for neutralization of the cleaner?
a) Sulfuric acid
b) Hydrochloric acid
c) Nitric acid
d) Sodium bicarbonate
15. Heat scale can cause what on the final finish?
a) Orange peel
b) high luster
c) Etching
d) Gas streaks
16. What components make up the electropolishing station?
a) Tank, heater, mist eliminator
b) Tank, heater, bussing
c) Tank, cathodes, 6V rectifier
d) Tank, anodes, transition piece
17. What is the preferred cathode:anode ratio?
a) 1:2
b) 2:1
c) 3:1
d) 4:1
18. What is the rectifier voltage required for Hydrite 4000 electrolyte?
a) 9V
b) 48V
c) 12V
d) 24V
19. What is the rule of thumb for metal removal?
a) 2000 AMP-MIN/Ft² removes 0.0001”
b) 1200 AMP-Min/Ft² removes 0.0002”
c) 1500 AMP-Min/Ft² removes 0.0005”
d) 2500 AMP-MIN/Ft² removes 0.0005”
20. Why is agitation used?
a) To control gas streaking
b) To distribute parts
c) To interrupt anodic film
d) To control voltage
21. A ¼” x 4” flat copper bar will carry how many amps?
a) 250 A
b) 500A
c) 1000A
d) 1500A
22. If a rectifier is operated at 50% output, what is the % ripple factor?
a) 1%
b) 5%
c) 50%
d) 27%
23. How do you correct for ripple factor?
a) Increase voltage
b) Increase current
c) Add choke filter
d) Remove some parts
24. Why are counter-flow rinse tanks used?
a) To get better rinsing efficiency
b) To reduce water consumption
c) To make use of atmospheric evaporator
d) All of the above
25. Why is there a nitric acid tank in the recommended process line?
a) To etch parts
b) to passivate parts
c) To remove by-products of EP solution
d) To create matte finish
26. What is the purpose of using hot DI water in the final rinse?
a) To remove sludge
b) To prevent spotting or staining
c) To remove oxidation
d) To create a DI coating
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