NACE Chp 3 Coatings Flashcards
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.
What are the 7 different solvent types
- Aliphatic Hydrocarbon Solvents
- Aromatic Hydrocarbon Solvents
- Ketone Solvents
- Ester Solvents
- Alcohol Solvents
- Ether/Glycol Ethers
- Miscellaneous Solvents
Paraffin is what kind of hydrocarbon solvent is it an open or closed chain?
Aliphatic solvents and they are OPEN chain or straight chain
Give 2 other examples of aliphatic hydrocarbon solvents?
- mineral spirits
2. V.M. and P (Varnish Makers and Painters) naphtha
What kind of boiling point does mineral spiriits have?
It has a HIGH boiling point and is used to dissolve oils, asphalts and alkyds
Benzol is an example of what kind of hydrocarbon solvent? Are they open or closed chain
Aromatic, they are CLOSED chain hydrocarbons
What is the six carbon ring called?
The benzene-ring structure.
What is the simplest chemical in this aromatic family of hydrocarbons?
Benzene; the family also includes TOLUENE, XYLENE, and some higher boiling point HOMOLOGS.
What solvents are oxygenated hydrocarbons of the acetone family?
Ketone solvents
Ketone solvents are the most effective for what materials
Vinyls. They are also often used in epoxies
a)What solvents have a banana-like odor? b) What kind of resins are they good solvents for?
a) Ester solvents.
b) Synthetic resins
What is the trade name of the best slow-evaporating solvent for thermoplastic acrylics?
Cellosolve
a) What solvents are good for highly polar binders such as phenolics?
b) Give 2 examples of these solvents
a) Alcohol solvents
b) Methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol or isopropyl alcohol
Why are ether solvents not usually used for synthetic resins?
They are very flammable
Cellosolve is used in many lacquers to improve what two things?
Flow out and gloss
Tetra hydrafuran is what kind of ether?
It is a cyclic ether with strong solvent characteristics for resinous materials e.g.rubbers, epoxies and acrylates
What is solution kick out?
The point at which the resin precipitates when a solvent is added to it in increasing amounts. Also known as the DILUTION LIMIT
What is the dilution limit an indication of?
The degree to which the resin and solvent are COMPATIBLE
What does VOC stand for?
Volatoile Organic Compounds
To make the calculation of the maximum allowable thinning that is VOC compliant, and inspector muct know what 4 things?
- Allowable VOC level
- VOC of activated/mixed coating
- VOC of thinner
- to calculate in ounces per gallon
SOLVENT SAFETY
What 2 kinds of hazards is solvent safety concerned with?
Fire and health
How is the flash point of a solvent defined?
AS the lowest temperature at which enough vapor will be present above the liquid to be IGNITED by an ignition source such as a flame.
The lower the flash has what effect on the vapor released and the risk of vapor ignition?
The GREATER the amount of vapor which will be released and the GREATER the risk of vapor ignition
The lower the flashpoint of a solvent makes that solvent more or less flammable?
The lower the flashpoint the MORE HIGHLY FLAMMABLE that solvent is
What is th lower explosive limit (LEL)?
It is the lowest concentration of solvent vapor in air that can be ignited
What is the upper explosive level (UEL)
It is the HIGHEST concentration of solvent in air that can be ignited.
What is the name of the Safety organization that deals with solvents?
The National Institute of Occupational Safety and Health (NIOSH)
What 2 things do they recommend inspectors use at all time when dealing with solvents?
Breathing apparatus and protectiv clothing
What does TLV stand for and what does it mean?
Threshold limit value: a concentration of airborne can be inhaled for a period of time by workers according to OSHA
What does TWA/TLV stand for and what does it mean?
Time weighted average/threshold limit value: time weighted average concentration for a stated work period e.g. 8 hour day or 40 hour week.
What does STEL/TLV stand for and what does it mean?
Short-term exposure limit/threshold limit value: The maximum concentration to which workers can be exposed regardless of the period of time.
What regulations should solvent storage follow?
Local and federal regulations
An inspector should notify the safety supervisor immediately if they have doubts about what 3 things?
- Any on-site solvent or coating handling practice
- Protective clothing
- Breathing apparatus
ADDITIVES:
What are 8 reasons additives are added to coatings?
- Adjust consistency
- Improve film build
- Make conductive (for use on concrete)
- Reduce settling
- Improve flexibility
- Retard mildew
- Provide anti-static properties to coating
- Provide abrasion and skid resistance
Additives are part of what portion of the coating?
The vehicle portion of the coating
