Coating Fundamentals Flashcards
A coating must exhibit a variety of properties to fulfill it’s role in corrosion control. Desirable properties include:
Chemical Resistance, Water Resistance, Ease of Application, Adhesion to Substrate, Cohesive Strength, Flexibility and Elongation, Impact Resistance, Temperature Resistance, and Dielectric Strength.
During coating formulation there is usually a ___-__ made among desirable properties.
Trade-off
The desirable properties of a coating alter when the ___ of the coating are changed.
Components
Coatings are classified as?
Organic or Inorganic
Most industrial and marine coatings are?
Organic Coatings.
Organic coating binders are made fro once living things. Most coatings now come from?
Refined Petroleum products.
All organic coatings contain?
Carbon
Inorganic coatings use inorganic binders, most commonly based on ___ or ___.
Silicone or Silicates.
Metallic Coatings (e.g. metallizing and galvanizing coatings) are?
Inorganic
Broadly speaking, the major difference between organic and inorganic coating is?
Heat resistance.
Organic coatings have less resistance to heat because of the relative weakness of the ___-___-___ bond.
Carbon-to-carbon bond.
Liquid-applied coating components are characterized by the terms?
Pigment
Resin/Binder
Solvent
Vehicle
A discrete particle solid used to impart specific properties to the coating in the liquid and solid state?
A Pigment
Pigments do not ___ in the coating and they serve multiple functions.
Dissolve
Pigments may be used to?
Impart Color, Protect the bider from weathering, provide inhibitor protection, control water resistance, provide a form of cathodic protection, or modify the mechanical or electrical properties.
The vehicle contains the?
Resin and Solvent
A coating consists of the?
Pigment and vehicle.
Additives are most commonly ___ ___ of a coating added in small amounts to perform a specific function.
Liquid components of a coating.
There are thousands of ___ and new ones presented frequently. These give each individual product its unique characteristics.
Additives
These give each individual coating product its unique characteristics.
Additives
Some additives keep the coating from settling, reduce foaming, retard color float and/or build thixotropy. These can all be described as?
Ensuring coating stability.
Additives may aid the coatings application by improving ___ ___ and wetting which, in turn, increases ___ ___ and decreases ___.
Flow out and wetting which, in turn, increases pot life and decreases sag.
Additives can aid in ___ Resistance.
UV Resistance.
Additives can increase/decrease?
Gloss
Additives can prevent ___ over in the can.
Skinning
Additives can retard or speed up?
Curing
Additives can increase shelf life. True or false?
True
Additives may also be considered a ___ ingredient.
Secret
The 1___ is the backbone of the coating ans supplies most 2___ ___ features and functions of the material.
Binder
Heavy Duty
A coating typically gets its name from the?
Binder
Epoxies, polyurethanes, alkyds, acrylics, etc are all?
Binders.
Multiple binders can be combined in a coating? True or False?
True
To create a protective film on a substrate the binder resins must convert from a ___ to a ___ state that adheres to and protects the surface.
Liquid to a Solid.
The liquid state of a coating allows for?
Application
In order to be suitable for use in a corrosion protection system in the industrial and marine environment, the binder should?
Have good wetting and adhesion properties.
Resist transmission of water, oxygen, and other chemical species.
Tolerate a variability in the application process.
Resist chemical and physical changes in the service environment.
Dry within an acceptable period.
Form a stable film that maintains it’s characteristic properties.
Strength, hardness and flexibility are all examples of possible ___ ___ of a coating.
Characteristic properties.
Some of the resins used as binders are ___ at normal temperatures.
Solids.
___ are added to liquefy the binder and allow for application.
Solvents.
Solvents have two major characteristics that influence their use in protective coatings.
Solvency Power & Volatility.
The ability to dissolve the resin is know as?
Solvency Power
___ governs the evaporation rate of a solvent.
Volatility
Once applied and cured ___ serve no purpose in a coating.
Solvents
___ may cause performance problems if they remain in the coating film.
Solvents
Because of environmental legislation, coating users and manufacturers are actively researching technologies to ___ or ___ the need for solvents.
Reduce or Eliminate.
The air pollution boards of many countries regulates the use of ___ in coatings.
Solvents
Organic solvents, known as ____ ___ ___, are harmful to the Earths Ozone layer.
Volatile Organic Compounds
Strict limits on the amount of solids used in coatings have led to a tremendous advance in the coatings industry. ___-___ coatings are used in many areas and new ___-___ or ___-___ coatings are being developed.
- Solvent Free
- Solvent Free
- High Solid
Improper field use of solvents causes many problems that can affect the coatings useful ___ ___.
Life Span
The coatings inspector should confirm that only the correct ___ is used and in the correct amounts allowed by the specification, local law, or MPDS.
Solvent
Corrosion control of coatings can occur in one of three processes:
Barrier coatings,
Inhibitive coatings, or sacrificial coatings (cathodic protection.)
A barrier coating impedes the ingress of ___, ___, and ___ ___.
Water, Oxygen, and soluble salts.
The barrier coating prevents the formation of an effective ___ at the coating/metal interface and restricts the access of the strongly depolarizing oxygen molecule.
Electrolyte
Water and oxygen penetrating to the substrate is not a significant issue if there are no ___ present on the surface. If they are present, however, corrosion does initiate.
Ions
During coating formulation, three mechanisms are thought to achieve barrier protection:
Resistance Inhibition,
Oxygen deprivation, and
Adhesion.
When subjected to scientific inquiry, scientists discovered that water and oxygen permeability of barrier coats were much higher than the levels at which corrosion is usually ___ and ___ on unprotected steel.
Initiated and sustained
The theory was proposed that the barrier films control corrosion by maintaining a high level of ___ ___ at, or near, the coating/substrate interface.
Electrical resistance
The high electrical resistance provided by barrier coatings prevents significant ___ ___ between anodic and cathodic areas. This phenomena reduces the potential for corrosion on the substrate.
Current flow
The high resistance of barrier coatings is maintained by films with low ___ to ___. I.e. resistance inhibition.
permeability to ions.
If ions are restricted via barrier coatings, the water that reaches the interface is not ___ to carry a significant ___ ___ to initiate and sustain corrosion .
Conductive enough to carry a significant corrosion current
If water and oxygen permeating the film to the substrate is NOT a significant factor if ions are not present in the surface. True or False
True
Formulations of barrier coatings can now modify the components of the coating for permeability to both ___ and ___.
Water and Ions
The generally accepted and simplified concept is that coatings provide a barrier between the ___ and the ___ (normally the electrolyte), thus removing one of the four required elements of he corrosion cell.
Substrate and the environment
Most coatings provide some element of ___ protection.
Barrier
Barrier coatings should exhibit the following attributes:
Resistance to the chemical environment,
Resistance to moisture,
Excellent adhesion to the substrate even in wet conditions,
Good wetting during application to prevent voids in th film and maximize effective surface area, and Resistance to vibration.
Inhibitive coatings, in addition to serving as a a barrier, actively slow down the reaction occurring at the ___ , the ___ or both.
Anode, cathode, or both.
To be effective, inhibitive coatings must be in ___ with the substrate.
Contact with the substrate. (i.e. be the primer)
Generally, Inhibitive coatings
- Have ___ added to the coating to hinder reactions on the substrate.
- Need a small amount of ___ to be activated.
- Chemicals
2. Moisture
Some inhibitive pigments, 1.___ and ___, have been eliminated in most markets. Yet other inhibitive pigments like 2.___ ___, ___, ___, and ___ are being used as inhibitors.
- Lead and Chromates
2. Zinc Phosphates, Metaborates, Molybdates, and Borosilicate’s
___ ___ actually passivate the metal surface by forming a thin, tightly adherent film. Or by reinforcing and plugging defects in the natural air-formed film. An example of such a coating is an alkyd based on zinc molybdates.
Inhibitive Pigments
Inhibitive pigments actually passivate the metal surface by forming a 1___, ___ ___ film. Or by ___ and ___ defect in the natural air-formed film.
- Thin, tightly adherent film.
2. Plugging and Reinforcing defects.
Inhibitive Pigments actually passivate the metal surface by forming a thin, tightly adherent film. Or by reinforcing and plugging defects in the natural air-formed film. An example of such a coating is an ___ based on ___ ___.
Alkyd based on Zinc Molybdates.
Sacrificial coating use a metal that is ___ to the steel and which corrodes preferentially.
Anodic
Essentially, sacrificial coatings provide ___ ___, especially in the vicinity of ___ ___.
- Cathodic Protection
2. Film Defects.
Sacrificial coatings usually contain ___ ___ as the predominant pigment.
Zinc Dust
Sacrificial coatings must have a ___ ___ of Zinc Dust to be effective.
Minimum Loading
Examples of Sacrificial Coatings include 1___ ___ and 2___-___ ___ (FSA).
- Inorganic Zinc
2. Flame-sprayed Aluminum.
The most basic function of any coating is its ability to ___ to the surface on which it is placed.
Adhere
___ ___ is the key to coating performance and long life.
Strong Adhesion
If adhesion is marginal, the coating gradually fails due to ___, ___-___ ___, or ___ and ___.
Blistering
Under-film corrosion
Chipping and Flaking
High levels of adhesion enable to coating to withstand ___, ___, ___, ___, ___, ___ and all the other factors it may be subjected to in service.
Abrasion Impact Flexing Humidity Chemicals Microorganisms
Adhesion can be ___, ___, ___ or a combination of all three.
Chemical, Mechanical
Polar
The chemical bond, formed by a reaction between the ___ and the ___ is the most effective Bond.
Coating and the Substrate
The most effective Adhesion bond is?
Chemical Adhesion
The galvanizing process is an example of what type of adhesion?
Chemical
A process in which molten zinc melts the surface layer of the steel and the two materials combine and form a series of alloys. Essentially making the coating a part of the surface?
Galvanizing
Inorganic zinc coating also form a ___ ___ between the silicate molecule and the steel substrate.
Chemical Bond
Wash primers that normally include an acid element form a ___ ___ with the substrate.
Chemical Bond
Inorganic zinc coating forms a chemical bond between the ___ ___ and the steel substrate.
Silicate molecule
Polar Adhesion is also known as?
Valance Bonding
The most common type of adhesion bond for organic coatings?
Polar Adhesion (AKA Valance Bonding)
In ___ ___ the resin acts as a weak magnet with the north and south poles attracting opposite poles on the substrate.
Polar Adhesion
In polar adhesion the resin acts as a weak magnet with the ___ and ___ south poles attracting opposite poles on the substrate.
North and South
Another explanation for Polar Adhesion is that the polar groups are ___ and ___ ___portions of the coating molecule that are attracted to oppositely charged areas on the substrate.
Positively and Negatively Charged
Epoxies fall within what type of adhesion concept?
Polar Adhesion (AKA Valance Bonding.)
Mechanical adhesion is associated with ___ ___. (Anchor pattern/profile)
Surface Roughness
The roughness of the surface created by some types of surface prep allows more points of contact between the ___ of the coating and the ___ of the surface.
Molecules of the coating and molecules of the surface.
Mechanical Adhesion: As the contact points of the surface 1___ so does 2___.
- Increases
2. Adhesion.
Concrete has a different type of ___ ___.
Mechanical Adhesion.
The concrete surface is relatively 1___ with many minute 2___ ___, ___ ___ and other natural surface roughness.
- Porous
2. Surface Pockets, surface checking
Coatings for concrete should be ___ ___.
Highly penetrating.
All forms of adhesion depend on direct contact between the ___ and the ___.
Coating and the Substrate.
Any type of contaminant on the surface interferes with ___-___-___ contact between the coating and the substrate and reduces adhesion.
Point-to-point.
The coatings inspector should check to see if the materials delivered to the job site are the materials shown in the 1___ or as approved by the 2___ or his ___.
- Specification
2. Owner or his representative.
The inspector should have a copy of each approved 1___ ___ ___ to compare the labels on the cans with the approved material.
Product Data Sheet.
Any substitution of an a material approved by the specification should be reported to?
The owners representative.
Be aware that even though two products may have the same ___ ___ they are not necessarily equal, or even equivalent.
Generic Name
The inspector should also check, (In regards to materials delivered to, or already on, the job site):
Shelf Life
Storage conditions and temperatures
Batch numbers. (Record these for each unit of coating.)
Batch numbers are always found on the ___ ___, not on the product data sheet.
Product pail/bucket.
It may be necessary to check each can, in each shipment, to ensure it is the ___ ___ and record batch numbers.
Proper material.
It is not unusual for a manufacturer to mix products on a pallet, or to ship the same product but from different batches, on the ___ ___.
Same Pallet.
When two component materials are used, the inspector should ensure that the correct 1___ of each component is on site, based on the 2___ ___.
- Amount
2. Mix Ratio.
The inspector checklist, with regards to materials is.
Specified materials on site.
Expiration date of coatings upon arrival on site.
Correct Colors
Correct and sufficient amounts of each component.
Legal and Protective storage conditions.
