Electroless Deposition Quizes

What is the normality of an acidic solution with a pH of 3.0?

The normality is 0.001

A 2 molar solution of H2SO4 contains _______g/L, while a 2N solution of H2SO4 contains_____g/L

196 and 98 grams per liter.

True or False: In water-based solutions, pH is defined by the equation pH = log [H+].

False

What is the correct formula for aluminum oxide if ionic aluminum has a valence of +3 and the valence of oxygen is -2?

Al2O3

True or False: The element, boron, is one of several elements that fall into the 'metals' category.

False.

What is the normality of the NaOH solution if a five mL solution is neutralized by ten mL of 1N H2SO4?

The normality of the NaOH solution is 2

Complete the Equation: NaOH + H2SO4 → Na2SO4 + H20

2NaOH + H2SO4 → Na2SO4 + 2H2O

Surface tension is produced because water molecules are

Polar

1 oz/gal = _______mg/L = ____________ppm (solution SPG = 1.0)

1 oz/gal = 7,500mg/L = 7,500ppm (Hint:1oz/gal = 7.5 grams)

Which of the following bonds are the strongest: covalent, ionic, chelated, or none of the above?

Chelated bonds are the strongest.

An acid is a substance that produces an excess of what ions when added to water?

Hydrogen ions.

A reaction tends to go to completion when: a) The product is ionized, b) The product is a gas and can leave the vessel c) The product is insoluble, d) All of the above?

D) All of the above.

What is the main purpose of a complexing agent in electroless nickel solutions? a)control the temperature of the solution b)prevent the formation of insoluble nickel compounds c)speed up the rate of deposition d)prevent gas pitting e)all of the above

B) To prevent the formation of insoluble nickel compounds.

What is the best choice for acid pickling of leaded brass? a)sulfuric b)fluoboric c)nitric d)nitric plus sulfuric e)none of the above

B) Fluoboric

Assuming the following valences: O = -2, H = +1, SO4 = -2, CrO4 = -2, In the reaction: 3H2SO3 + 2H2CrO4 → Cr2(SO4)3 + 5H2O, which atom is reduced and which is oxidized?

a) hydrogen is oxidized and oxygen is reduced b)chromium is reduced and hydrogen is oxidized c)chromium is oxidized and oxygen is reduced d)chromium is reduced and sulfur is oxidized e)sulfur is reduced and chromium is oxidized

D) Chromium is reduced and Sulfur is oxidized.

The reducing agent for producing an EN-P deposit is:

The reducing agent is sodium hypophosphite.

High phos EN-P typically contains more than what percentage of P?

More than 10% P

High Phos EN is typically used for its a)solderablity b)weldability c)appearance d)ductility e)all of the above f)none of the above

F) None of the above

Medium phos EN is typically employed for what? a)best corrosion resistance b)best solderability c)best combination of corrosion resistance, wear and economy d)best heat treatability e)all of the above f)none of the above

C) Best combination of corrosion resistance, wear, and economy.

Low phos Ni is typically employed for a)best corrosion resistance b)best solderability c)best heat treatability d)all of the above e)b and c

E) B and C

Alkaline EN processes may be employed for a)best corrosion resistance b)plating on plastics c)best heat treatability d)plating over zincated aluminum e)B and C f)B and D

F) B and D

The most basic ingredients of an EN-P solution are which components? a) Nickel sulfate or nickel chloride plus lead acetate b)Nickel sulfate or nickel chloride plus boric acid c)Nickel sulfate or nickel chloride plus sodium hypophosphite d)Nickel sulfate or nickel chloride plus thiourea e)none of the above

C) Nickel sulfate or nickel chloride plus sodium hypophosphite.

Which metal surfaces are not catalytic in a common EN solution reduced with hypophosphite? a)steel b)zincated aluminum c)nickel d)copper e)none of the above

D) Copper

True or False: Traces of lead or thiourea have historically been used as stabilizers in common EN-P solutions.

True.

When EN-P or EN-B is heat treated at the proper temperature and for the correct amount of time, which of the following changes occur to the deposit: _____a. Deposit is softer than as plated and amorphous in structure______b. Deposit is harder than as plated and better in corrosion resistance______c. Deposit contains an intermetallic between nickel and phosphorus (or boron)______d. Deposit is lower in corrosion resistance than as plated______ e. a and b ______f. c and d

F) C and D

True or False: Common reducing agents for producing Ni-B include sodium borohydride and dimethyl sulfonic acid (DMSA).

False

True or False: Sodium borohydride can be used to deposit Ni-B from an EN solution at pH 5

False

Surfactants that may be employed in electroless nickel plating solutions are either cationic or a)sulfurized b)anionic c)catatonic d)non-ionic e)none of the above

B) Anionic

Composite EN-P-PTFE coatings typically contain between ___ and ____ % by volume of PTFE particulates

18 - 25 %

True or false: Immersion plating and electroless plating are the same process.

False

Excessive concentration of stabilizer can cause a)low plating speed b)low corrosion resistance c)edge effects d)skip plating e)all of the above

E) All of the above

True or false: Some buffers that may be part of an EN formulation can also act as complexing agents

True

18. Using nickel hypophosphite instead of sodium hypophosphite has the following advantage:_a. higher plating speed_b. higher corrosion resistance_c. introduces no undesirable ions__d. no skip plating__e. none of the above

C) Introduces no undesirable ions

19. If an aluminum or zincated part is to be EN-B plated, the borohydride solution might:_a. be the best choice__b. chemically attack the parts_c. plate slower than the DMAB solution_d. produce a soft deposit_e. none of the above

B) Chemically attack the parts

A deposit produced from an amine-borane EN-B solution may be excessively stressed if the thickness is greater than about ____ microns

5 microns

True or False: The density of an EN-P or an EN-B deposit is increased as the alloy increases in phosphorus/boron content.

False

True or False: While the phosphorus in EN-P deposits is typically uniformly dispersed, the boron in EN-B deposits tends to be non-uniform.

True

True or False: The cauliflower-like surface of EN-P deposits partially explains the high level of wear resistance, since the gaps between the bumps can retain lubricants.

False

In comparing the salt spray performance of EN-P with EN-B, 10-25 microns of a 5^th generation EN-B deposit tends to:__a. perform better than high-phos EN-P _b. perform as well as high-phos EN-P _c. perform better than low and mid-phos EN-P _d. perform worse than any EN-P deposit _e. none of the above

C) Perform better than low and mid-phos EN-P

True or False: While heat treating EN-P deposits typically reduces corrosion resistance, at temperatures greater than 600ºC, a dense intermetallic may form at the substrate-plating interface and actually enhance corrosion resistance.

True

True or False: EN-B deposits tend to resist corrosion better in neutral or acidic environments vs. those that are alkaline.

False

True or False: A part that has a rough surface may require 50-100% more plating vs. one that has a smooth surface.

True

The impact on the fatigue strength of an EN-P plated part is dependent upon:__a. %P _b. plating thickness _c. thermal treatments, if any __d. a and b but not c __e. a, b and c _f. none of the above

E) A, B and C

True or False: Because EN-B deposits are generally compressively stressed, they do not impact the fatigue strength of an EN-B plated part.

False

True or False: In general, EN-P deposits display a harder “as plated” condition vs.  EN-B deposits.

False

True or False: The as plated hardness of EN-P goes down if the %P goes up.

 

True

True or False: The as plated hardness of EN-B goes down if the %B goes up.

False

True or False: Based on data from the Nickel Development Institute, the heat treatment temperature for obtaining the maximum hardness of an EN-P deposit should be adjusted based upon the %P.

True

True or False: Based on data from the Nickel Development Institute, the heat treatment of an EN-4%B deposit should be conducted in less than 20 minutes, if the temperature is 400-500ºC.

True

True or False: Adhesion of EN deposits over aluminum can be enhanced by baking 1-4 hours at 400-550°C. 

False (In Fahrenheit yes, but NOT Celsius! Tricky question!)

16. Which is more ductile?__a.  EN-10%P __b.  EN-5%B __c. they are equally ductile

A) EN-10%P

Which of the following composite EN deposits can match the Taber Wear Index of hard chromium?

____a. EN-P + Silicon carbide

____b. EN_P + aluminum oxide

____c. EN-P + boron carbide

____d. EN-P + diamond

____e. all of the above

____f. none of the above

E) all of the above

True or False: the internal stress of an EN-P deposit can be compressive, if it is very low or very high in %P

True

True or False: In general, EN-B deposits are typically lower in internal stress vs. EN-P deposits.

False

True or False: EN-P and EN-B deposits typically lose all of their magnetic properties when the %P and the %B exceed 6.4% in concentration.

False

The minimum total surface area to volume of electroless plating solutions is:

1.2 to 1.8, need at least 6-12 inches of solution around a part you are plating

What are the common plating tank materials of construction:

Polypropylene, stainless steel, and steel (with bag)

What is the pore size for filtration of an EN process solution?

1 Micron

What are the methods of heating EN solutions?

Immersion heater and external heater

At what size are exterior supports needed for polypropylene tanks?_______ gallons.

50 Gallons

What are some simple energy conservation devices for EN tanks?

Insulating the tanks - keeps heat in, and a cover on top of the tank (must be polypropylene, tanks lose a lot of heat from the top surface).

Which of the following materials should NOT be used for long term service piping on an EN process tank?____  (a) CPVC ___  (b) Polypropylene ____  (c) glass ____  (d) Kynar® ____  (e) Stainless steel ____  (f) polycarbonate

 

C and F

The purpose of agitation of an EN solution is to

Sweeps away hydrogen gas bubbles that may cause pitting, makes sure the solution is constantly getting mixed ensuring there aren’t hot spots, the chemicals aren’t sitting stagnant after adds, and keeps particulates moving to help filter particles in tank.

Is carbon filtration of an EN plating solution a good idea? When?

No. Only when the chemicals say you need to.

What are the benefits of automated analysis and control of an EN process?

Improved consistency, and it essentially removes all human error. Less rejects, monitors PH, very easy to control and see where levels and temps are at. It’s also great for record keeping, as it records temps and makes it easy to check past information.

The basic preparation ‘secret’ for aluminum is what?

Zincate.

What is the activation process for stainless steels or nickel alloys?

Degreasing if necessary, and a nickel strike.

What is the best first plated layer over zincate?

Alkaline EN.

4. When cleaning a part, the best location for ultrasonics is: ____a. the EN solution

____b. the soak cleaner

____c. the acid pickle

____d. none of the above

 

D) None of the above

True or False: The zincate formulation that is used for magnesium is the same as for aluminum.

False.

Name three of the control parameters of a zincate for aluminum?

Temperature, time, and rinsing.

True or False: Magnesium can be plated without a zincate.

True

True or False: When plating magnesium without a zincate the EN plating solution needs to be modified in chemistry

True

True or False:  The EN plating solution formulation for plating magnesium without a zincate contains fluoride(s). 

True

True or False:  Periodic reverse cleaning does not expose high strength steel to hydrogen.  

False

True or False: Beryllium is treated using a zincate as part of the preparation cycle.

True

True or False: Zinc die castings typically have buffing compound on the surface 

True

Which of these acids would you chose for pickling zinc die castings:_____ 2% vol sulfuric _____ 2 %vol nitric _____ 2%vol Hydrochloric

2%vol Hydrochloric

A major problem with powder metallurgy is: _____ a. Surface Passivity

_____ b. Surface porosity

_____ c. Surface oxides

_____ d. None of the above

B) Surface porosity

The acid in most any EN stripping solution is most likely _____________. 

Nitric

Which of the following acids would you use to strip EN off aluminum? _____ 50% vol sulfuric

_____ 50%vol nitric

_____ 50%vol Hydrochloric

50%vol nitric

Activation process for tungsten may employ an etch in hot ____________.

 

KOH

As taught in this lesson, molybdenum may be electrolytically etched using

_____ a. a chromic acid solution

_____ b. KOH

_____ c. nitric-phosphoric

_____ d. none of the above

A) A chromic acid solution

Pure Mo can be activated using a cathodic activation treatment in___________________ acid followed by a sulfamate nickel strike.

sulfamic

 If a steel part needs repetitive stripping of EN, the acidic solution most likely to be used probably will contain ___________________ acid.

chromic

True or False: Some high strength steel and heat treated Be-Cu alloys require stress relief baking before stripping defective EN deposits.

True

Powder metallurgy parts that exhibit surface porosity may be treated with _____ a. chromic acid

_____ b. KOH

_____ c. vacuum impregnation

_____ d. none of the above

C) Vacuum impregnation

According to BAC 5771, hydrogen sensitive parts should be relief baked within _____ hrs. of stripping.

24 hours

True or False: Adhesion of EN deposits on titanium substrates is improved by thermal treatment at 390ºC.  

False

1. What is the most commonly employed reducing agent for EN-P?____ a. Nickel chloride

____ b. Nickel sulfate

____ c. Nickel acetate

____ d. Nickel orthophosphite

____ e. None of the above

E) None of the above (the answer is sodium hypophosphite).

What is the main advantage to using nickel hypophosphite as the reducing agent?

____ a. Lower cost

____ b. lower carbon footprint

____ c. no need for a complexing agent

____ d. contains no undesirable anion

____ e. None of the above

D) Contains no undesirable anion

If the Ni content drops below about 4g/L in an EN-P solution, the most likely effect on the process is: ____ a. increased plating speed

____ b. increase in the %Ni in the deposit

____ c. decrease in %Ni in the deposit

____ d. increase in the brightness of the deposit

____ e. None of the above

C) A decrease in %Ni in the deposit

A complexing agent that has a high stability constant has what effect in an EN-P process:____ a. increases the %Ni in the deposit

____ b. decreases the %Ni in the deposit

____ c. decreases the stability of the solution

____ d. increase in the brightness of the deposit

____ e. None of the above

C) Decreases the stability of the solution

Operating an EN-P solution at the high end of the pH range:

____ a. increases the %Ni in the deposit

____ b. decreases the %Ni in the deposit

____ c. decreases the plating speed

____ d. increases the plating seed

____ e. a and c

____ f. a and d

____g. None of the above

 

E) A and C

True or False: Some EN-P complexing agents also act to buffer the pH

True

Which of the following is a stabilizer?

____a. Lead acetate,

____b. lead sulfide,

____c. thiosulfate,

____d. thiourea,

____e. molybdic acid 

____f. thiocyanate

____g. All of the above

G) all of the above

Even if an EN-P solution contains a stabilizer, the plated parts may develop edge pull-back if:

____a. the stabilizer is lead acetate,

____b. the pH of the EN solution is too high

____c. the agitation level is too low 

____d. the agitation level is too high 

____e. the solution is air agitated 

____f.  the solution has no agitation

____g. none of the above

D) the agitation level is too high

An a typical EN-P solution, incorporation of a surfactant into the solution formulation has which of these effects:

____a. reduces pitting tendency

____b. increases plating speed

____c. produces a much harder as-plated deposit 

____d. produces a much softer as-plated deposit 

____e. none of the above 

____f.  a and b

____g. a and c

F) A and B

True or False: Brightener for typical EN-P solutions fall into two categories; organic or inorganic.

True

True or False: Typical EN-P solutions can tolerate a higher concentration of orthophosphite at the higher end of the operating pH range.

False