NACE Chp 3 Coatings Flashcards
(58 cards)
What is the definition of a “coating?
A film forming material that protects the surface it’s applied to from the effects of the environment
What are the 2 classifications of coatings
Organic(made from living things) and Inorganic(uses an inorganic binder)
Give 2 examples of ORGANIC coatings
tung, oil, castor oil, linseed oil, fish. All contain CARBON
Give 2 examples of INORGANIC coatings
SILICATES: sodium silicate, calcium silicate, lithium silicate, ethyl silicate(organic)
What are the 2 components of coating?
Pigment and Vehicle
What are 2 qualities of pigment
- pigment is a discrete particulate solid used for protection and decoration
- they do not dissolve, they remain in particles
What else does pigment describe?
Pigment can also describe inert fillers like chalk, talc, mica added for bulk
What part of the coating is the vehicle?
Vehicle is the liquid base of the coating.
What 3 things does vehicle consist of?
- Solvent
- Binder (resin i.e the film-forming portion)most coatings are named after the resin binder
- Liquid additives
What 2 components make up the dried coating film?
The binder and pigment
What are the 5 functions of pigments? (In total there are 6 main functions and 6 other functions)
1.it’s rust inhibiting 2 makes film less permeable 3 hides the surface 4 color 5 protects from UV rays and weather 6 reinforces the film 7 self-cleaning and controlled chalking 8 helps with coat binder drying 9 Helps with paint storage 10 increases body so thicker films can be applied 11 allows sacrificial protection 12 provides finishes…metallic or glosses
What are the 3 different pigment shapes and what is each used for?
- Nodular- LUMP SHAPED-generally adds COLOR or are SACRIFICIAL
- Acicular- NEEDLE-SHAPED- e.g. zinc oxide- adds COLOR and REINFORCES
- Lamellar- PLATELIKE-e.g. mica, glass flake-makes MORE IMPERMEABLE to moisture
What does vehicle consist of?
- Solvents
- Binders (resins)
- Additives
What are the 2 component groups of vehicle?
- Nonvolatile, film-forming (binder)
2. Volatile solvents
How are coating materials generally named? Give 2 examples
Coating materials are generally named for their PRINCIPAL RESIN
Examples epoxy, vinyl etc.
What do most resins require to aid in their application?
Solvent
What must binders convert from and into to create a protective coating?
The binder resins must convert from PLIANT LIQUID FORM to COHESIVE SOLID FORM
What properties should a binder have to be a suitable corrosion resistant coating?
(there are 6 in total)
1 Have good WETTING and ADHESION properties
2 resist water and oxygen transmission
3 Tolerate different application processes
4 Resist chemical and physical change
5 dry in reasonable time to avoid any contamination
6 form a stable film but still be flexible and strong
What is seen as the most critical choice in coating selection?
Choice of BINDER
What are the 3 classifications of solvents and their properties
- Primary (active): dissolves the resin that allows its use as a coating vehicle
- Latent: used with the primary solvent to:
- make the coating easier to apply
- control the evaporation rate
- improve quality of the final film.
- Diluent: e.g.water used with active solvents to dilute the coating in the container. Diluents DO NOT dissolve the resin.
What are the 2 characteristics of solvents?
- Solvency power: the ability to dissolve other chemical compounds (e.g. resins)
- Volatility: largely governs the evaporation rate
In reducing the coating for application, what is the ONLY solvent that should be used?
ONLY the SOLVENT SPECIFIED in the coating specificatrion
Name 5 things that EVAPORATION RATE influences
- leveling
- flowing
- sagging
- wet-edge time
- gloss
Evaporation rates are usually expressed relative to what?
the n-butyl acetate, which has a flsh point of 38 degrees and is assigned a value of one.
