FROSIO考试99个问问答

The 99 questions What condition is essential for galvanic (bimetallic) corrosion to occur? Oxygen; electrolyte; (two metals having) different potentials 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