End Of Chapter Study Guides Flashcards
Define corrosion
The deterioration of a metal that results from a reaction in the environment.
What is passivation?
A reduction of the anodic reation rate of an electrode involved in corrosion.
What are the elements of a corrosion cell?
Anode
Cathode
Return path
Electrolyte
Describe what happens at the anode.
Oxidation occurs at anode. Electrons flow away from anode in the external circuit. Corrosion occurs at anode and metal ions enter the solution at the anode.
What is the function of the electrolyte?
The electrolyte must be present to close the loop in the corrosion cell. The corrosion current is carried by ion transport through the electrolyte.
What is the function of the metallic pathway?
Connects the anode to the cathode and allows a passage of electrons from anode to cathode.
What is the galvanic series?
A list of materials in order of their corrosion potentials, with the most active at the top and the least active at the bottom.
The general rules of galvanic corrosion are:
When dissimilar metals are connected, the most active metal corrodes faster while the least active metal corrodes slower.
As the potential difference between the metals increase, the rate of galvanic corrosion increases.
Five factors that affect the rate of corrosion
Oxygen Temperature Chemical salts Humidity Pollutants and Acid Gases
General corrosion is
relativelt uniform loss of material over the entire surface and is a general thinning of affected surface.
Localized corrosion is
Occurs at discrete sites on the metal surface.
List some of the common tools/methods for corrosion control.
Design Inhibitors Material selection Cathodic protection Protective coatings Alteration of the environment
How does NACE define the inspector’s role?
Quality control technician who observes and reports technical aspects of coating project. Observe, test, verify, report.
What is the inspector’s responsibility when it comes to safety on a project?
Safety enforcement is not the inspector’s responsibility. Be knowledgeable of safety violations.
Tests that may need to be conducted during surface preparation and coating operations.
Relative humidity and dew point. surface temperature. surface contaminants. proper abrasive media. cleanliness of abrasive. check air compressor. Air supply to blast hose. Blast nozzle for size and wear. Blasted surface for anchor pattern. Viscosity of coating. Application equipment. DFT of each coat. Surface contaminants.
Documentation/reports that may be required to be maintained on a coatings project.
Daily written report. Inspection logbook. Routine report. Notes from weekly progress meetings. Any reports required by client.
Most important characteristics of a good report?
Objective, accurate, detailed.
What is the inspector’s primary responsibility and what should the inspector not do as it pertains to the specification.
The inspector’s primary responsibility is to VERIFY the specification. The inspector does not make changes to the specification for any reason.
What type of information do you find on a Product Data Sheet?
Manufacturer’s Product Data Sheet answers questions about coating product. Application methods, surface cleanlinesss, parameters, temperatures, curing times.
What type of information do you find on a Safety Data Sheet
Toxicity Health Effects First Aid Reactivity Storage Disposal PPE Spill Handling Procedures
Explain the difference between Quality Assurance and Quality Control
QA - Checks whether the product or service is meeting specified requirements.
QC - Product or service is meeting the requirements of the client.
Identify some defects that can be caused by incorrect temperature applications
Blistering Pin holing Cratering Dry spray Mud cracking
Describe Relative Humidity
A measure of the amount of moisture in the air compared to saturation level.
What is the dew point temperature?
Temperature which moisture begins to form on a steel surface.
Name some of the effects wind may have on a coating project.
Blow abrasives past the boundaries of the work area.
Cause drift or overspray of sprayed coatings.
Accelerates solvent evaporation.
Formation of dry spray.
What are some of the common errors when using an electronic hygrometer?
Reading taken in direct sunlight.
Instrument was left in place for too long.
Instrument removed before stabilized.
Calibration or equipment malfunction.
Explain the process for use of the sling psychrometer.
Saturate sock with clean water.
Whirl the instrument rapidly for about 40 seconds.
Read the wet bulb temperature.
Repeat process until the temperature stabilizes.
Once wet bulb is stabilized, record the dry bulb temperature.
List 3 desirable properties of a coating.
Chemical resistance. Water resistance. Ease of application. Adhesion to substrate. Cohesive strength. Flexibility and elongation. Impact resistance. Abrasion resistance. Temperature resistance. Dielectric strength.
The 2 broad classifications of a coating are:
Organic coating
Inorganic coating
What are 2 primary components of a liquid applied coating?
Pigment
Resin/Binder
Solvent
Vehicle
Describe 3 methods by which coating provides corrosion control.
Barrier - impedes ingress of oxygen, water, soluble salts
Inhibitive - slows down reaction occuring on substrate.
Sacrificial - anodic metal that corrodes preferentially.
What are 3 different ways a coating can adhere to the surface?
Chemical
Mechanical
Polar
The 2 broad classification for curing mechanisms are:
Nonconvertible
Convertible
List 2 nonconvertible coating types.
Vinyl
Chlorinated Rubber
List 3 convertible coating curing mechanisms.
Oxidation
Co-reaction (polymerization)
Hydrolysis
Fusion
List 2 characteristics of oxidation cure coatings
Cure by reaction of atmospheric oxygen.
Not suitable for immersion.
3 coatings types that cure by polymerization.
Epoxies Urethanes Polyureas Polyaspartics Polysiloxanes
Induction time is:
Time required between mixing the coating and application.
What is the main requirement for a hydrolysis coating to cure?
Moisture.
Industrial and marine coatings are commonly referred to by:
Generic Resin Type
Oil based coatings applied over alkaline surfaces may result in
Saponification
List 5 of the formal sections usually contained in a good specification.
Scope of work Terms and definitions Reference standards and codes Safety Pre-job conference Coating materials Sampling coatings Workmanship Application Work schedule Repairs and remedial coating work Inspection Documentation
What are 2 of the inspector’s responsibilites as it relates to the specification?
VERIFY the specification.
Do not change the specification.
During surface preparation, surface cleanliness should be inspected at a minimum the following 3 times:
Before any surface preparation activities.
After surface preparation, before coatings begin.
Between each application in a multi-coat system.
Factors during surface preparation that may effect service life include:
Residues of oil, grease, soil. Residues of chemical salts. Rust on the surface. Loose or broken mill scale. Rust scale. Anchor pattern. Defects mechanical cleaning equipment. Surface condensation. Old deteriorated coatings. Incompatible existing coatings.
Common design defects include:
Hard to reach/inaccesible areas. Rivets, bolts, or other connectors. Welds. Gaps/skip welds. Overlapping surfaces. Angles, complex arrangements. Threaded areas. Dissimilar metals. Sharp edges/corners/rough cut plate. Construction aids.
Common fabrication defects include:
Weld splatter.
Skip welds.
Rough welds.
Sharp corners and edges.
4 typical SSPC SP1 pre-cleaning methods include:
Solvent wipe with cloth or rag. Immersion of the substrate in solvent. Solvent spray. Vapor degreasing. Steam cleaning. Emulsion cleaning. Chemical paint stripping. Use of alkaline cleaners.
1 standard for use with power tool cleaning is:
SSPC SP11
4 examples of tools used for power tool cleaning are:
Rotary wire brushes Impact tools Needle scaler Rotary scaler Piston scaler Grinders and sanders Disc sanders
2 abrasive blasting methods include:
Centrifugal blasting Sand-injected water blasting Slurry blasting Wet abrasive blasting Dry grit (air) blasting
Visual standards for abrasive blasting include:
SSPC-VIS1
SSPC-SP10/NACE2 limits staining to ___ per each unit area.
5%
SSPC-SP5/NACE1 limits staining to ___ per each unit area.
NONE
SSPC-SP6/NACE3 limits staining to ___ per each unit area.
33%
The 2 types of abrasive blasting nozzles include:
Straight Bore
Venturi
The specified level of surface cleanliness must be achieved and maintained:
Immediately prior to coating applications.
Advantages of centrifugal blast equipment include:
Dust and fines are contained.
Abrasives are recyclable.
Blasting and priming can be done inline operation.
General overall economy.
No compressors, piping, or air handling equipment needed.
The inspector’s checklist for surface preparation should include:
Ambient conditions Conditions of substrate Pre-blast surface cleanlinesss Shot/grit size selection Shot/grit cleanliness Abrasive blasting equipment Surface profile Surface cleanliness after abrasive blasting Operator qualifications Safety
Abrasive media types include:
Shot/grit metallic Crushed slag Ceramic grit Silica sand Garnet Agricultural abrasives Specialty abrasives
Abrasive media typically used for recycling include:
Steel shot
Steel grit
List the pressure ranges that categorize: Low pressure Water Cleaning High pressure water cleaning High pressure waterjetting Ultrahigh pressure waterjetting
<34 MPa 5000 PSI
34-70 MPa 5k-10k PSI
70-120 MPa 10k-30k PSI
>210 MPa 30k PSI
3 types of water blasting include:
Grit Blasting with Shroud
Sand Injected Water Blast
Slurry Blast Grit/Water Mix
The visual guide for use with the NACE-SSPC waterjetting standard is:
SSPC VIS 4
NACE VIS 7
3 test methods for surface profile include:
Comparator and Coupons
Replica Tape
Digital Gauge Depth Macrometer (profilometer)
Types of soluble salt contamination include:
Chlorides
Sulfates
Nitrates
If inspection is to be effective with regards to soluble salts, the specification should very clearly state:
Limits to be accepted Specific salts to be limited Test method to be used Frequency of testing Locations in which tests should be administered
Tests for soluble salts include:
Bresle Patch
Sleeve Test
Soluble Salt Meters
Conductivity Meters
Depth of surface profile can be evaluated by several methods:
ISO Comparator
Replica Tape
Digital Profile Gauge
The ISO comparator grades may be recorded:
Finer than fine grade Fine grade Medium grade Coarse grade Coarser than coarse grade
2 types of replica tape that are commonly used:
Coarse
Extra Coarse
List the standards for using the replica tape
NACE Standard RP0287
ASTM D 4417
ISO 8503-5
When using replica tape, common errors include:
Variation in point-to-point profile over the surface being tested
The presence of particles of dirt on either the replica tape or gauge
Gauge accuracy
The rubbing or burnishing technique
Goals of a pre-job conference include:
Discuss health, safety and environment (HES) Requirements
Address/ clarify emergency procedures
Review and discuss scope of work (SOW)
Review logistical support
Discuss line communications between parties
Review known critical hazards
Establish list of critical point of contacts (POCS)
Discuss and clarify inspector (s) responsibilities and authority
Clarify the chain of command (Reporting System)
Discuss and Clarify areas of concern in the project specification (Omissions, clarifications, testing)
Agree on critical hold points for inspections
Conflict resolution between the inspector and applicator
Change orders
People who may be required to attend the pre-job conference include:
Owner Owners contract manager Engineer Specifying Engineer Operations personnel Specifier Purchasing agents Coatings manufacturer (Preferably tech. service representative) Coating inspector (s) Project safety personnel Coatings applicator (Supervision personnel)
Before the start of the pre-job conference, the inspector should obtain a copy of, read, and understand the :
Specification
Any standard / Procedure referenced in the project
Manufacturer’s product data sheets MPDS
Safety Data Sheet
Documentation may include:
Detailed written daily reports Inspection logs Routine Reports Reports for weekly progress meetings Daily entries in a project log book A daily inspection report using standardized forms Routine Reports Monthly or quarterly reports
Inspection records show:
Environmental conditions Pretreatment Details Cleaning details Materials Details Coating applications Details Results of work and all tests
Good records allow management to:
Detect and tag design defects for future work
Evaluate coating performance
Determine annual cost data on each coating system
Develop ongoing maintenance program
Project inspection documentation provides:
Inspection (QC) records
Management information
Verification of work performed by the contractor
Details of non-conforming work
One guide to enclosures for coatings projects is
SSPC Technology Update #6
SSPC Technology #16
Low temperature concerns during coatings application include
Slow the curing of chemically curing coatings
Increases viscosity
High temperature concerns during coatings application include
Solvent evaporates too quickly
Pot life decreases
Viscosity decreases
Tired workers
High humidity during coating application may
Slows solvent evaporation
Leaves moisture on coating surface
Coating reacts to moisture instead of resin causing blushing
May effect gloss or color
Coatings may be applied by the following methods
Roller Brush Airless spray Conventional spray High volume low pressure Air assisted airlesss spray
Coatings Product Data Sheets (coating spec) provide users with the following:
Surface preparation Storage Mixing and thinning Application procedure DFT requirements
SDS contains the following:
Provides workers and Emergency personnel with the critical information on composition, handling or working with the substance
Includes information such as MELTING POINT, BOILING POINT, FLASH POINT, TOXICITY, HEALTH EFFECTS, FIRST AID, REACTIVITY, storage disposal, protective equipment, and spill handling procedures.
Provides information regarding the safety issues associated with any hazardous ( or potentially hazard) material
Provides Instructions for the correct action to take in the event of a spill, explosion, fir or hazardous exposure.
Non-drying films (failure to cure) may be caused by:
Not adding curing agent, Wrong curing agent or incorrect amount of it
Problem with material from the manufacturer
Environmental issues (too cold, hot, or humid)
Wrong or contaminated thinner (Solvent)
Some of the problems that can be caused by amine blush are:
Surface tackiness or greasiness Incomplete curing Poor adhesion Coating Discoloration Poor gloss rentention
Runs, sags, and wrinkles may be caused by:
Applying the coating too thick Too much or the wrong thinner used Surface too hot to apply the coating Application of coating at the end of its pot life Wrong thixotrope used in manufacturing
____ is a powdery, friable layer on the surface of a coating that is most common with epoxy coatings.
Chalking
Cratering may be caused by:
Air trapped in the coating and forming a bubble which then bursts
Air trapped in the coating during mixing if the proper procedures are not followed
Voids are typically caused by:
Running the mixer too fast
Pinholes are:
Very small holes in a coating typically cause by air or solvent trapped in porous film and escaping.
A common cause of blistering is:
Surface contamination under the applied coating
Cracking of a coating is noted:
When the crack extends to the substrate.
Checking can be described as:
Fine cracks in the surface of a coating that don’t extend through the substrate
Adhesion failures may be caused by:
11/11 Fine cracks in the surface of a coating that don't extend through the substrate Checking can be described as: Contamination on the surface Wrong surface preparation specified Failure to inspect surface preparation Insufficient surface profile Exceeding the topcoat window Application of incompatible coatings
General types of holiday detectors include
Low-voltage DC
High-voltage DC
High-voltage Pulse DC
High-voltage AC
Low voltage (wet sponge) holiday detectors are powered by a battery with output voltages ranging:
5 to 120 V DC
Descrive low voltage (wet sponge) holiday detectors:
Wet sponge detector
Sensitive, low voltage
Ground cable
5-120V DC Battery
High voltage DC holiday detector types include:
DC Pulsed
DC Constant Current
Describe high voltage DC holiday detectors
Ground cable to metal or ground
800 to 6k volts
Constant current for dielectric coatings
Pule current for moist conditions
What is a standard?
An established norm or requirement that is written by industry professionals
A formal document that establishes uniform engineering or technical criteria, methods, processes and practices
What percentage of NACE standards relate to coatings?
50%
