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NACE CIP1 > Chapter 14-15 > Flashcards

Chapter 14-15 Flashcards

1
Q

Summarize the relationship between drying and curing

A

“drying = removal of solvent by evaporation , cannot stand up to minor scratches bumps or other damage
curing = chemicals process in which the coating crosslinks to reach its optimum hardness”

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2
Q

“drying = “

A

removal of solvent by evaporation , cannot stand up to minor scratches bumps or other damage

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3
Q

curing =

A

chemicals process in which the coating crosslinks to reach its optimum hardness

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4
Q

convertible and non convertible coatings

A

“2 types of curing mechanism
Non-Convertible Coating - no chemical change , can be re-dissolved in solvent used/ single component coatings / aka Thermoplastic - can be reheated, remolded and cooled.- typically single coats

Convertible - cure through a chemical change as a result of an irreversible cross-linking reactions / aka thermoset - coatings that strethen when heated will not resoften after the inital cure. cannot be redissolved by their orignal solvent - typical multicoat/single coats . Chemical cure”

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5
Q

Non-Convertible Coating -

A

no chemical change , can be re-dissolved in solvent used/ single component coatings / aka Thermoplastic - can be reheated, remolded and cooled.- typically single coats

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6
Q

Convertible -

A

cure through a chemical change as a result of an irreversible cross-linking reactions / aka thermoset - coatings that stregthen when heated will not resoften after the initial cure. cannot be redissolved by their original solvent - typical multicoat/single coats . Chemical cure”

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7
Q

Non convertible - solvent evaporation (vinyl and chlorinated rubber)

A

“1. no chemical change
2. when the solvent evaporates from the applied film into the air, the resin pigment, and additives remain on the surface.
3. permanently dissolvable in their own origianl solvents, care needs to be taken not to overcoat these types of coatings with coatings containg aggressive solvents without first apply a test patch to veriyf.
4. must not apply to thick or will trap solvents within the film
5. rapid solvent evaporation can be prone to dry spray and cobwebbing.
6. solvent evaporation contains VOC.
“

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8
Q

Non convertible - coalescence (latexes or acrylic and water emulsions)

A

“cure through evaporation of water combined with the fusing together of the resin/binder particles
1. tiny particles of resins are dispersed in the water
2. when water evaporates the resin particles fuse together (coalesce) to form a continuous film
3. requires a min of 50F, if under 50F curing may stop and may not start again.
4. not good for immersion service,
5. should not be top coated with strong solvents .
6. too high tem can cause caoting to dry too quickly on the surface and blister “

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9
Q

Convertible - oxidation (alkyds, drying oils,)

A

“1. once the solvent evaporates, these coating cure by reaction with o2. the oxidation process never stops as long as the coating is exposed to oxygen.
2. typical single coating
3. environmental concerns - high temp decreases curing time
4. overcoat - application to an alkaline surface can cause adhesion isses (galvanized metal) - SAPONIFICATION (form soap)
5. excessive film build - can prevent oxygen from permeating through the enter film”

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10
Q

Convertible - co reaction cure (vinyl ester, polyester, urethanes, polyureas, polyXXX, epoxies,fluropolymer )

A

“1. cure by cross-linking at least 2 chemicals (polymerizations)
2. 2 component coating comes in 2 separate containers a base and a hardener or catalyst.
3. pot life
4. mixing ratios - worng mixing ratios
5. mixing the overcoat windows - top coating “

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11
Q

Convertible - fusion ( silicone high temp coatings and bake phenolic coating)

A

“1. curing a coating film through the additon of heat
2. baking or cooling schedule may be needed
3. temperature - need to follow bake and heat schedule to complete cure.”

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12
Q

Convertible - hydrolysis (inorganic zinc and mositure/single cure polyurethanes)

A

“1. absorb humidity from surround air to complete the curing process.
2. req min of 40% RH”

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13
Q

Non convertible - solvent evaporation

A

(vinyl and chlorinated rubber)

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14
Q

Non convertible - coalescence

A

(latexes or acrylic and water emulsions)

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15
Q

Convertible - oxidation

A

(alkyds, drying oils,)

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16
Q

Convertible - co reaction cure

A

(vinyl ester, polyester, urethanes, polyureas, polyXXX, epoxies,fluropolymer )

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17
Q

Convertible - hydrolysis

A

(inorganic zinc and mositure/single cure polyurethanes)

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18
Q

Convertible - fusion

A

( silicone high temp coatings and bake phenolic coating)

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19
Q

cure through evap of water combine with the fusing together of resin/binder particles

A

coaleascence

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20
Q

Cure by cross linking (polymerizzation) at least 2 chemcials

A

co reaction

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21
Q

Require some amount of moisture vapor in the surrounding air for the coating to cure

A

hydrolysis

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22
Q

Cure by reaction with atmospheric oxygen once the solvent evaporates

A

oxidation

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23
Q

Require a particular temp to complete the cure

A

fusion

24
Q

no chemical change occurs during evap of solvent

A

solvent evaporation

25
Q

describe the inspectors role during and post curing (5)

A

“1. Read the spec and identify the required film thickness
2. Read the PDS and determine the required environmetal conditions and dry/curing times, recoat intervals
3. Mesure environmental conditions throughout the curing process to ensure they are within allowable ranges
4. Verify that each coating layer has cured for the min time but has been overcoated before exceeding the max recoat time
5. Conduct any post-cure test required by the specification”

26
Q

curing is influenced by

A

“1. environmental conditions
2. applied film thickness
3. mixing of the coating “

27
Q

colder temp requires longer cure times
higher air temp can accelerate solvent evaporation and reduce recoat windows
High RH may cause solvent entrapment
Wind can accelerate solvent evaporation
stay <85% RH during curing
dry best at 56-99 F

A
28
Q

set to touch coating is tacky not adhere to finger
dry to touch coating does not rub up when the finger is lightly rubbed across the surface
dry hard no evidence of thumb pressure in film
dry through (dry to handle) no evidence of loosening , detachment, wrinkling

A
29
Q

Describe what a premature coating failure is and the inspector’s role in preventing it

A

premature failure occurs when coating fail before their intended service life is over, inspector role is to perform a series of tasks to verify that the installation of the coating system was a success.

30
Q

Identify common coating defects and describe their potential causes (5)

A

“1. Inadequate Surface Prepartion = ~70% of failure
2. Incorrect coating system slection
3. Improper Mixing and Thinning
4. Failure to monitor environmental Conditions - when outside the specified range, the quality of the applied coating cannot be assure.
5. Poor application Technique and Curing Management”

31
Q

Explain what dry film thickness is and its bearing on coating failure

A

“DFT is a measure of the thickness of a coating system once all solvents have evaporated and the coating has cured.

32
Q
  1. Adhesion Loss, Flaking, Delaminatin, and Peeling -
A

due to surface contamination, poor surface prepartion, insufficient surface profile, aged coating

33
Q
  1. Coating Failures - cracking and checking -
A

cracking refers to cracks that do not penetrate the top coat - due to surface movement , aging, excessive coating thickness

34
Q
  1. Fisheyes -
A

separation or pulling apart of wet film leaving small, crater - like holes or indentation - due to inadequate surface prep, contamination , use of the incorrect solvent

35
Q
  1. Blistering, lifting of a coating film away from the substrate, as of result of
A

adhersion failure due to substrate contamination, solvent entrapment, trapped moisture between coats, high humidity and high surface temp

36
Q
  1. Cratering -
A

formation of small, uniform bowl shaped depression due to escape of trapped air.

37
Q

blistering

A

adhesion failure due to substrate contamination, solvent entrapment, trapped moisture between coats, high humidity and high surface temp

38
Q

amine blush

A

a flat, milky, white or clear haze or mist formed on the surface of the film that is common in amine cured epoxy coatings - due to air temperatures are cooling and RH is rising, condensation or mositure during or after application.

39
Q
  1. Chalking - powdery, friable layer on the surface due to
A

exposure to weathering or UV light degradation - most common in epoxy coatings

40
Q
  1. Dry Spray -
A

rough or uneven finish in the paint film, where particles are not fluid or flowing togethers due to improper application technique, rapid evaporation of solvents , incorrect thinner

41
Q
  1. Failure on welds, sharp edge, and edge -
A
42
Q
  1. Mud Cracking -
A

deep, irregular cracks, due to excessive film thickness, common with IOZ >6mis

43
Q
  1. Pinholes -
A

air or gas bubbles that brust when air or solvent escapes due to poor surface praration or wrong solvent selection, solvent or air entrapment

44
Q
  1. Runs, sags, wrinkles and curtains -
A

due to excessive film thickness, coating viscosity too high or too low, too much thinner

45
Q
  1. Non- Drying Film (Failure to Cure) -
A

due to excessive thickness, wrong thinner, or not adding curring agent

46
Q
  1. Alligatorting -
A

large crazing due to application of a hard, tough coating over a softer, extensible coating, curing rapidyly relative to the underlying coating

47
Q
  1. Orange peel -
A

failure of a coating film to flow out which creates a pebbled appears due to nap cover , excess film thickness,

48
Q

“Too thick -

A

reduce flexibility, wrinkling, cracking and improper curing

49
Q

too thin - i

A

increase moisture or chemical permeation , premature failure, uncoated peaks, and discontinuities+C69”

50
Q

Explain what holidays are and how they can contribute to coating failures “Holidays - any defect where there is a discontinuity in the coating film. Part of the surface remians uncoated due to low film build due to poor inconsistent application technique, lack of stripe coating.

A

Crater
Crack
Pit
Skip
Pin-Point Rust
Pinhole
Fisheye”

51
Q

Low Voltage DC used for coating

A

less than 20mils

52
Q

Amine Blush Testing (2)

A

Brush Swab Test
pH Test “

53
Q

milky white, yellow, or gray appearance, tacky nature can lead to dirt or debris pick-up
ofte amine blush can appear clear and is diffcult to see. Use shinning a flashing light to look for shiny and flat spots in the sheen

A
54
Q

When Polyurethanes are applied at an excessive thicknes, the isocyanate within the coating material mixes with the mostiure in the air creating CO2 gases. This cases bubble to form

A
55
Q

false holidays in

A

not yet cured coatings

NACE CIP1 (8 decks)

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