The 99 questions
1. What condition is essential for galvanic (bimetallic) corrosion to occur?
Oxygen; electrolyte; (two metals having) different potentials
2. How do we recognize turbulence corrosion?
In copper we can find sharply defined pits which commonly are undercut on the side facing the water’s direction of flow
3. When we use the term degraphitation of cast iron, what kind of corrosion do we refer to ?
Selective corrosion
4. Degraphitation is a special form of bimetallic corrosion and either iron or the steel is consumed
through dissolution. Which of the two substances will go to dissolution?
Iron (will sacrifice itself for graphite leaving the surface as a layer. This layer has no
mechanical strength, however the object looks intact. The graphite may be easily removed with
e.g. a knife.
5. Most of coatings function by the barrier principal. Against what is the coating barrier?
(against) liquid; water and partly oxygen
6. Dose a coating heavily pigmented with zinc phosphate provide corrosion protection by the
galvanic principle?
No, by inhibitor principle
7. Why is a surface profile important to adhesion of a coating system?
It enlarger the area to contact, providing anchorage
8. How do we check surfaces for a metal cleanliness of sa3 ensure that all soluble substances are
removed from the surface?
According to ISO 8502-6 and ISO 8502-9.
Sampling (“ Bresle method”) and measure the conductivity.
9. Will blasting steel surface to a metal cleanliness sa3 ensure that all soluble substances are
removed from the surface?
No, it can only remove partly.
Fresh water washing will do it.
10. What must be done to the steel surface before grinding?
Steel preparation first (removing weld slag/weld spatter, chipping off lamination), then
removing oil/grease and/or water soluble substances by solvent cleaning and/or HPW washing
11. Why is a steel surface, which has been burnished through rotary wire brushing not a very
good surface to apply paint?
It is too much smooth, there is no good adhesion between the coating and the surface
12. What is the function of a moisture separator on a compressor?
To separate water from the compressed air
13. What is the effort of increasing the distance from the blast nozzle to the surface?
It will loss kinetic energy (shallow roughness/poor blasting)
14. Which angle (the blasting nozzle to surface) should you select when blasting off most parts of
thick, which is well adhesion epoxy mastic system?
45 to 60 degree angle
15. What problem connected to the paint system’s service life can you get if you use an inhibitor
in connecting with water jetting?
Give later osmotic blistering and affect the adhesion between the paint and the substrate.
16. Is water jetting suited for primary surface preparation? If you think so, please state why? If
you think not, please state why?
No, it is only suited for secondary surface preparation, because it dose not create good
surface roughness
17. If, after blasting, flash rust appears rather more quickly than usual, what could indicate?
There is water soluble substance on surface; there is condensation on surface; the humidity is
high
18. What is the lowers liquid pressure according to the joint SSPC/NACE standard that is
designated water jetting
70 Mpa (10000 psi)
19. What is laitance?
It is the outer crust of freshly cast concrete.
20. Where can you find information such as the pot life of a coating?
In the product data sheet.
21. When paints are stored for long periods of time, what component settles to the bottom?
The pigment will settle to the bottom
22. How can you get rid of air that has been mixed into liquid paint before application?
Put is a while, the air will release the air by itself in the induction time
23. What effects do the temperature has on the pot life of paint?
If the temperature increase, the pot life will reduce; if the temperature reduce , the pot life will
increase.
24. When would you use a moisture/oil trap between an air compressor and the pressure pot in an
air spray unit?
The moisture / oil trap would be always used when you an air spray unit
25. Why dose paint “wrap around” to the sides and the back of an object during electrostatic spray
application?
The paint is given an electrostatic charge (usu. negative), the object is earthed, the negative
charged paint particles are attracted to all parts of object and the build up of paint is especially
good on edges.
26. What degree of metal cleanliness is required for thermal spraying of a metallic coating, and
what should the surface profile be?
Sa3 and 50-80 um
27. Which metals are the ones most commonly used in thermal spray application?
Aluminum alloy and zinc alloy
28. What is induction time?
Some paints need to sit for a while prior to use in order for the two components to start
reacting, this period of time is called induction time
29. What effect will hot weather have on the pot life a chemical curing coating?
Hot weather will shorten the curing time
30. What is a pot life?
When the two components paint is mixed, it only has a short period of time between the
Mixing point and the point at which the paint cured, can not be used anymore , this period of
Time is called pot life.
31. What is a water borne coating?
In a water borne coating the organic solvents are almost absent, and the binder, in form of
small spheroids is dispersed in water.
32. What effect will low temperature and high humidity have on the drying/curing of water borne
coating?
There will be condensation on the coating surface, the coating may not dry/cure
33. “water borne coating dose not contain any solvent at all”, Is this a correct statement
This is not correct. Water borne coating contain a small amount of special solvent—
plasticiser (usu. < 6%)
34. What effect will increasing the solids content of a coating have on the VOC level of a coating?
The VOC will be lowered
35. What effect will thinning have on the film building properties of a coating?
It will lead sagging /runs; you will increase the WFT in order to achieve the specified DFT
36. What dose SSPC-SP10 designate?
Very through blast cleaning—near white metal blast cleaning
(ISO sa2 1/2)
37. On a work site you find that the wind is blowing steadily at apace 15 miles per hour. Will this
affect airless spray application of zinc ethyl silicate?
Yes, the velocity is too high. The maximum permit is 7.2km/hr
38. Why should the steel temperature during blasting or paint application be at least 3 *c above the
dew point?
Avoid condensation to ensure good adhesion
39. How do we determine if a blasted steel surface the required metal cleanliness or not?
You can determine by using the standard ISO 8501-1 (with photos)
40. What does P Sa3 designate?
Partial (localized) blasting to sa3 to a previously coated surface.
41. And P St 2 ?
partial (localized) hand or power tool cleaning to st2 to a previously coated surface.
42. What is the difference between a specification and procedure?
A specification tells what will be done, a procedure tells how will be done.
A specification comprise the elements necessary to describe the result aimed at.
A procedure must cover all aspects of the work –not only surface preparation and application.
43. “Reporting is demanded to make life difficult for coating advisers and ensure that they do not
go to bars and loose women” is this statement correct? Please justify your viewpoint
regardless of weather or not you agree with the statement?
No, I do not agree with it. Reporting is very important, everything should be written down
clearly so that we can find the reasons easily if some troubles happen.
44. Why is it necessary to remove grease from a surface prior to blast cleaning?
For blast cleaning will not fully remove the grease, instead, it will spot the grease everywhere.
45. When you have removed lead containing paint from surface through grinding should you then
take your work clothes home and wash them by hands?
No, throw them away.
46. What is the flash point?
Flash point is the lowest temperature at which a liquid liberates sufficient vapor to form a
mixture with the air near its surface which, if ignited, will make a small flash, but not catch
fire.
47. How do we check the surface profile achieved on a cleaned surface?
Compare with standard ISO8503
48. How long shall you twirl a sling psychrometer in order to determine the wet and dry
temperature?
Do not stop until the two thermometers stable.
49. If you use a worn nozzle on an airless spray gun, how will this affect the thickness of the wet
film deposited on the surface as compared to an identical but unused nozzle?
High film thickness/maybe sagging/orange peel/
50. What should you do if your receive a shipment of coatings which have exceed their pot life?
Return them back, report accordingly.
51. What do we mean by theoretical coverage?
It is defines as the area of surface that can be covered at uniform specified dry film thickness
by a specified unit volume of a coating in theory.
52. Why do we specify a certain dry film thickness for a coat of paint?
PLS listen to the professor.
53. What check would you be likely to make to find the cause of fish eye in a paint film?
Oil/grease, silicone, dirt
54. What is the main causes of the below paint film defects?
Wrinkling: a. Too thick
b. weather too warm
Orange peel: a. Paint too viscous
b. gun too close
c. too fast solvent evaporation
d. too low air pressure.
Pinhole: a. Solvent/air passage through the film
b. insufficient atomization
c. coarse atomization
d. settled pigment(s)
Dry spray: a. Gun too far away
b. too high atomization
c. incorrect spray technique
d. fall-out from wind
e. too high air temperature
Sagging: a. gun too close
b. too much paint (slow pass)
c. excess thinning
d. surface too hard/glossy
e. surface temperature too high
f. surface temperature too low.
Flaking: a. Contamination on the substrate to be over coated
b. condensation on substrates at time of application
c. the underlying substrates is too hard and glossy.
55. Where do you find the requirements for personal protection gear for spray application of a
polyurethane paint?
In safety date sheet
56. If somebody on the job accidentally swallows paints, what do you do then?
Sent him to hospital immediately, and give the safety date sheet to the doctor.
57. What do we mean with the term TLV?
Threshold limit value. It is a guideline for the assessment of the hygienic standard of
atmosphere in the work environment.
58. Why dose your cigarette taste so strange when you smoking in an atmosphere which contains
solvent fumes ?
It contains explosion/phosgene gas.
59. What is the maximum size of dust particles, which may enter your lungs if you do not use a
filer mask?
5 mm
60. Inside a confined space, where do solvent vapors collect ?
In the bottom.
61. What protective gear will you use when entering a tank, which cannot be tested for oxygen
level or presence of toxic gases?
Full mask with oxygen cylinder.
62. Which three factors are essential for general corrosion to take place?
O2,electrolyte and difference in potential
63. What is the formula for calculating the DFT when you know the wet film thickness and the
volume solids of paint?
DFT=WFT x volume solid %
64. Please name three function pigment may have in paint formulation.
a. color b. Gloss c. Anti corrosive d. UV protection e. Give “body “ to paint
f. mechanical strength
65. Please list three advantages and three disadvantages connected to airless spray.
Advantages: high application speed/high film thickness/good penetration
Disadvantages: costly/dangerous/not for small detail uses
66. Please give two reasons for applying passive fire protection to steel structure.
a. secure escape route for personnel
b. secure integrity and stability of structure
c. retard spread of fire
67. Why is it impossible to measure the DFT of a coat of prefabrication primer on steel plates that
have been blasted?
a. the DFT of prefabrication primer is low (15—25um)
b. the prefabrication primer is flexible.
68. a) What is the adhesive failure?
Loss of adhesion between coats or between paint and substrate.
b) Please list reason for adhesive failure.
The surface has been contaminated; (chemical curing paint) the over coating time exceeded
the specified requirement.
c)what is cohesive failure?
It is the inside break of film.
d) Please list reason for cohesive failure?
Vacuoles, water, oil or others in film
e) what method do we have for testing the adhesive and cohesive properties of paint system?
By ISO 4624 (pull-off test)
69. Please explain how the standard ISO 8501-1 is organized.
You can make drawings (28 photos)
70. What do we call that property which prevents high coating from sagging?
Thixotropy
71. Please name the two most important pigments used in prefabrication primer.
Zinc/iron oxide
72. What do we mean by the term dry to touch?
It is surface dry, it is not yet dry to handle.
Put some small glass balls on the surface of the paint, if the balls can be moved by the
sweeping of brush and the balls are not contaminated by paint, it means the paint is touch dry.
73. Please name on chemically curing, inorganic one-component paint.
Cement based coating/
74. Why do we not in general use magnesium anodes to protect the underwater hull of ships?
Magnesium will sacrifice too fast.
75. How many square meters will a liter of 100% solids paint applied to a DFT of 1 um cover
theoretically?
1000 m2
76. What is electrolyte?
Electrolyte is liquid which is electrically conductive.
77. Are electrons emitted from the anodes or from the cathode in a galvanic circuit?
From the anodes
78. Are iron ions positively of negatively charged?
Positively
79. What is thinner?
Solvent or mix of solvent to adjust the viscosity
80. What do we mean by a generic type?
Generic type: coatings with the same type of binder and active filler (EG. ZN)
81. What is the function of a concrete sealer coat?
Prevent water oxygen and oil from penetrating into the concrete and get good adhesion.
82. Please explain what we mean by PH-scale.
It is the expression of some substance to be acidic or alkaline.
0---------------------7------------------------14
acidic medium alkaline
83. Please name three abrasives used for centrifugal blast cleaning of steel.
Steel shot ,steel grit and steel wire cut
84. Please name the three principles for drying/curing paint.
Physically drying, oxidative curing , chemically curing
85. Please name one example of a generic type of paint from each of the three groups you have
listed 84 above.
Acrylic paint, alkyd paint, epoxy paint
86. What do we mean by functionality in the resin of a chemical curing paint?
Please listen to the professor
87. Please name three main components in a paint formulation.
Binder, pigment and solvent
88. What is osmotic blistering and why dose it occur?
Soluble salts, if present on a substrate at time of application of paint systems, will later cause
osmotic blistering because of osmotic pressure.
89. Why is vital to move the spray gun parallel to the substrate when applying paint by spray?
In order to get a even film on anyplace of the surface.
90. What problems with the paint film can be expected when you hold the spray gun 80cm away
from the work piece?
Open film / dry spray / uneven film / no good adhesion
91. In which standard can we find information about classification of corrosive environment?
ISO 12944-2
92. How do we check if a two component epoxy coating has cured sufficiently for over coating
with a polyurethane topcoat?
Check the over coating time from the product date sheet.
93. Please name the three principles by which paints steel from corrosion.
Barrier, galvanic and inhibitor
94. When a specification demand a metal cleanliness of minimum Sa 2.5 what does this mean?
At what time shall the metal have this cleanliness?
a. Very through blast cleaning – near white metal blast cleaning
b. Just before start application
95. what does the standard ISO 8502-9 cover?
Measuring the conductivity.
96. After having carried out an adhesion test by pull-off method you find both the dolly and the
pulled off area on the steel to be covered with a pink primer. What kind of break does this
signify?
“cohesive break”
97. You spill some epoxy thinner on the deck of a ship and you observe that the existing coating
system becomes wrinkle on the surface. What can this tell you about the existing coating
system?
Oxidative cured paint (alkyd)
98. How will solvent affects you brain acute affect?
Intoxication
99. What contamination can you reveal on the surface by lighting it up by means of an ultraviolet
light bulb?
Oil contamination.
