Quality Control of Industrial Painting Operations

William D. CorbettKTA-Tator, Inc.

Webinar Content• Industry standards for coating application QC• Developing a quality control plan for painting• Navigating a Technical (Product) Data Sheet• Measuring ambient conditions and surface temperature• Witnessing mixing, thinning and application procedures• Calculation and measurement of wet film thickness• Dry film thickness measurement• Post-application testing

Cure/hardnessHoliday/pinhole detectionAdhesionIdentifying application defects

Learning Objectives/Outcomes

• Completion of this webinar will enable the participant to:

Describe the industry standards that pertain to coating application Prepare a Quality Control Plan for painting Describe the content of a Technical (Product) Data Sheet Measure environmental conditions and surface temperature prior

to coating mixing Evaluate mixing, thinning and application procedures Calculate and measure wet film thickness Measure dry film thickness Perform post-application testing

Industry Standards for Coating Application

• SSPC-PA 1 Shop, Field and Maintenance Painting of Steel• SSPC-PA 2 (frequency and tolerance of coating thickness

measurements on steel)• SSPC-PA 9 (frequency and tolerance of coating thickness

measurements on concrete)• ASTM E337 (use of whirling/aspirating psychrometers)• ASTM D4414 (wet film thickness measurement)• ASTM D7091/D6132 (dry film thickness measurement)• ASTM D5402/D4752/D3363/D1640 (drying, curing, hardness)• ASTM D5162/D4787 (holiday/pinhole detection)• ASTM D3359/D6677/D4541/D7234 (adhesion)

SSPC Paint Application Specification No. 1 (PA 1)

• Shop, Field and Maintenance Painting of Steel• Common specification reference• Contains 14 Sections:

1. Scope 8. Shop Coating2. Description 9. Field Coating3. Referenced Standards 10. Repair of Damaged Coatings4. Definitions 11. Appl. Proc. For Coatings5. Pre-application Procedures 12. Curing & Handling6. Factors Affecting Application 13. Inspection7. Application Methods 14. Safety & Environmental

Purpose of a Quality Control Plan

• Provides QC Inspector with:A systematic inspection and testing plan that

covers all phases of work in sequenceA written document that lists what to inspect, how

to inspect and the acceptance criteriaA tool to enable an inspector to navigate through

and extract inspection check points from the specification

• May be a required contract submittal

Benefits of a Quality Control Plan

Coating specifications can be complex documentsSpecifications typically contain the quality

requirements for a coatings projectGood inspection doesn’t happen by accident; it

requires planningQC plans make specification compliance more

streamlined and completeProvides a key communication tool between QA

and QC inspection personnel

Inspection Item

Technique/Instrument

Frequency of Tests

Standard Test

Method Reference

Spec.Referenc

e(mock)

Acceptance Criteria(mock)

Verify ambient conditions

Electronic psychrometer

Before mixing and every 4 hours; changing conditions

SSPC-PA 1 3.4.1 Air: 50-100°FSurface: 50-110°FRH: <85%ST > 5°F DP

Verify installation of protective coverings

Visual Prior to primer application

SSPC-PA 1 3.4.2 Properly installed & maintained

Dry Film Thickness of Primer

Calibrated Type 2 gage verified for accuracy

Area coated during the previous work shift, per SSPC PA2

ASTM D 7091SSPC-PA2

3.4.7 3-5 mils

Holiday Detection

Low voltage wet sponge detector

After topcoat application

ASTM D5162 3.4.10 No pinholes or holidays

Sample Quality Control Plan

Product Data Sheets

Prepared by the coating manufacturer

An “instruction manual” for the coating

Technical & marketing information about the coating

ASTM F 718 provides a standard specification for marine paints

Product Data Sheets, con’t.

• Typically contain:Brand name of the productGeneric type of the coatingWhen/where the coating can be usedCompatible coatingsProduct weight and volume solids contentTheoretical coverage rate

Product Data Sheets, con’t.Often contain:

Recommended level(s) of surface preparationRecommended dry film thicknessVOC content of the coating (as manufactured)Adjusted VOC content dependant on amount and type of thinnerPerformance data (adhesion, abrasion resistance, etc.)Recommended methods of applicationMixing and thinning instructions Pot life, induction time Drying times (dry to handle, dry to recoat) Cure times Recoat times Method to verify cure

Product Data Sheets Vs. Specification Requirements

• Product data sheets contain recommendations• When the PDS and the project specification differ,

the specification is the governing document (contract)• The specification may invoke the PDS• QC inspector should note discrepancies/vague

information and advise the owner at the bidding stage and at the pre-job meeting

Environmental Conditions for Coating Application• Air Temperature (min. &

max.)

• Relative Humidity (min. or max)

• Dew Point Temperature

• Surface Temperature [min.

5 °F (3°C)] above Dew Point Temperature

• Wind Speed (max.)

Significance of Conditions

• Air TemperatureToo cold or too hot can affect coating application &

curing

• Relative HumidityToo damp or too dry can affect coating application &

curing

• Surface TemperatureToo cold or too hot can affect application & curing

• Surface temperature at or below dew point temperature will result in condensation

Significance of Conditions, con’t.

• Wind SpeedToo windy can affect application (dry spray) and cause

overspray damage

• Mixing/application of coatings under adverse weather conditions can void the manufacturer’s warranty and is considered a specification non-conformance

Ambient Conditions & Surface Temperature• Measuring Instruments

Sling Psychrometers*Battery-powered

Psychrometers*Electronic PsychrometersAnalog, Thermocouple-

type & Non-contact Surface Thermometers

* Used in conjunction with psychrometric charts or calculators

Sling Psychrometer

Using Sling Psychrometers

• ASTM E337• Verify wick cleanliness• Saturate wick and/or fill

reservoir with DI water• Whirl 20-30 second intervals

until wet bulb stabilizes (2 readings within 0.5o)

• Record wet & dry bulb temperatures

Using Psychrometric Charts

• Locate Chart (relative humidity or dew point)

• Verify Barometric Pressure (e.g., 30.0 in.)

• Intersect air temperature with wet bulb depression (Ta-Tw)

• Calculators (bottom image) can also be used

Electronic Psychrometers• Measure/Record:

Air Temperature Surface Temperature (ST) Relative Humidity Dew Point Temperature (DP) Spread between

DP and ST

• Features Auto-logging allows for automatic

data collection Magnetic surface probe Data graphing and Blue Tooth

uploading Audio/visual alarm

Measuring Surface Temperature

• Dial-Type ThermometerPosition & stabilize for

minimum of 2 minutes

• Thermocouple-Type ThermometersStabilize quickly

• Infrared (non-contact) thermometersWatch distance

Assessing Wind Speed

• Analog wind meters• Digital wind meters• Rotating Vane

AnemometersAir flow inside

containmentWind speed

Documenting Ambient Conditions and Surface Temperature

ConditionCondition DataDataDateDate 2/15/122/15/12

TimeTime 0900 hours0900 hours

Dry Bulb Temperature (DB)Dry Bulb Temperature (DB) 1616ooC (60C (60ooF)F)

Wet Bulb Temperature (WB)Wet Bulb Temperature (WB) 1313ooC (55C (55ooF)F)

Depression (DB-WB)Depression (DB-WB) 33ooC (5C (5ooF)F)

Relative HumidityRelative Humidity 73%73%

Dew Point TemperatureDew Point Temperature 1111ooC (51C (51ooF)F)

Surface TemperatureSurface Temperature 1515ooC (59C (59ooF)F)

Wind SpeedWind Speed 11 km/Hr (7 mph)11 km/Hr (7 mph)

Measurement LocationMeasurement Location West side of tank, ground levelWest side of tank, ground level

Significance of 5°F (3°C)

• Theoretically, a small (<1°F) increase (surface temperature over dew point) will preclude moisture formation

• Minimum increase of 5°F (3°C) compensates for: Instrument tolerances Varying conditions Changing conditions

Location and Frequency of Data Acquisition• Location

Dictated by where the work is being performed (e.g., inside vs. outside of a containment; balcony of elevated storage tank vs. ground level)

If interior, with ventilation in operation

Shops: Blast or Paint bay area

• FrequencyPrior to mixing of

coatingsFour-hour data collection

intervals is commonMore frequent

measurement if conditions are changing

Inspecting Mixing Procedures

1. Verify components are within the manufacturer’s shelf life (and stored properly)

2. Check PDS for mixing instructions

3. Measure coating temperature after all components are thoroughly blended

4. Straining required?

5. Thinning required/allowed?

6. Induction time required?

7. Pot life monitoring

Inspecting Thinning Procedures

• Verify:Correct type of thinner is

usedCalculation of thinner

quantity is accurateGraduated containers are

used to measure thinner

• Consider impact on local VOC regulations

Calculating the Target Wet Film Thickness

• Sometimes the wet film thickness will be listed on the PDS (many times it is not)

• Arriving at the target wet film thickness is necessary to arrive at the specified dry film thickness

• Must be adjusted based on the amount of thinner added

Calculating a Target Wet Film Thickness

• Calculating Target Wet Film Thickness

WFT = Target DFT% solids by volume

Example: 5 mils DFT68% solids by volume (0.68)

Target wet film thickness: 7-8 mils

Calculating a Target Wet Film Thickness

• Effect of Thinner Addition on WFT Target

WFT = Target DFT

% solids by volume

100% + % thinner

Calculating a Target Wet Film Thickness• Effect of Thinner Addition, continued

WFT = 5 mils DFT

0.68

100% + 20% thinner

5 mils DFT 5 mils DFT

68 = 0.57 = 9 mils WFT

120

Measuring Wet Film Thickness

• ASTM D 4414 – “Practice for Measurement of Wet Film Thickness by Notch Gages”

• Place gage into wet coating immediately

• Withdraw gage and read highest wetted step (e.g., 5 mils)

• Immediately clean coating from gage

Measuring Dry Film Thickness

• Three common standards that address the nondestructive measurement of coating thickness : Ferrous and nonferrous metals: ASTM D 7091 Steel only: SSPC-PA 2 (2004)

2012 version will address ferrous and nonferrous metals

Non-metal surfaces ASTM D 6132SSPC-PA 9

Measuring Dry Film Thickness

• Standards provide procedures for:Calibration (gage manufacturer/approved lab)Frequency of verifying gage accuracy (user)Frequency of measurements (number of

measurements to obtain based on the size of the structure)

• SSPC-PA 2 places limits on spot and area readings vs. specified thickness

Measuring Dry Film Thickness (SSPC-PA 2)

• Requires calibration by manufacturer (typically annual)

• Certificate of calibration traceable to a National Metrology Institute required

• Verification of accuracy (by user) before and after each period of use

• Two types of nondestructive coating thickness gagesMagnetic pull-off (Type 1)Electronic (Type 2)

Verifying Type 1 Gage Accuracy

• Use calibration blocksNIST TraceableProprietary from gage

manufacturers

• Verify accuracy: In range of useBefore and after each period

of use

• Must correct for surface roughness (BMR)

Verifying Type 2 Gage Accuracy

• Use calibration blocks or shims

• Verify accuracy in range of useMost can be adjustedFollow gage

manufacturer’s instructions (vary)

Verification of Type 2 Gage Accuracy

• If smooth reference standards are used (A), user must correct* for surface roughness

• If shims (foils) are used (over the prepared steel; B), no correction is needed

*Via Base Metal Reading (BMR)

A B

Measurement Frequency

• Terminology:Gage Reading: A single reading at one locationSpot Measurement: The average of at least 3 gage readings

made within a 1.5” diameter circle

Area Measurement: The average of 5 spot measurements made within a 100 square foot area

Measurement Frequency

Dividing Structures into Test Areas

• If the structure is less than 300 square feet, each 100 square feet is measured

• If the structure is between 300 and 1000 square feet, select 3 random 100 square foot test areas and measure

• For structures exceeding 1000 square feet, select 3 random 100 square feet testing areas for the first 1000 square feet, and select 1 random 100 square foot testing area for each additional 1000 square feet

Example:

Structure Size: 55,000 square feetNo. of Areas: 3 + 54 = 57 areas

No. of Spots: 57 Areas x 5 Spots/Area = 285 Spots

No. of Gage Readings: 285 Spots x 3 Readings/Spot = 855 Gage Readings

Coating Thickness Tolerance (SSPC-PA 2)

• Individual readings (averaged to create a spot measurement) are unrestrictedNon-repeating low or high readings can be discarded

• The spot measurement (the average of 3) must be within 80% of the minimum thickness and 120% of the maximum

• Area measurement must be within specified range

Assessing Intercoat Cleanliness

• Airborne dust and/or abrasive may be deposited on coated surfaces

• Problematic if surface is to be recoated

• Requires visual or tactical (touch) examination of the surface

Verifying Recoat Times and Temperatures

• Coating materials may have a minimum and/or a maximum recoat time

• Verify:Coating has been allowed to dry or cure the

minimum amount of timeThe next coat is applied before the maximum

recoat time has been exceeded

Detecting Pinholes and Holidays• Definitions:

Holidays – skips or misses in the coating/lining system Pinholes – tiny voids in the coating or lining

• Standards:ASTM D5162 and D4787; NACE RP01-88

Conducted:After final coat has been applied, but before it has achieved complete cure (touch-up)Specifications may require holiday testing after the application of each coat

May cause intercoat contamination

Rules for Holiday Detection

• Coating must be nonconductive

• Substrate must be conductive

• High voltage (spark) testing requires voltage setting100 to 125 volts/mil of coatingObtain recommended test voltage from coating

manufacturerExcessive voltage can damage coating film

Holiday Detectors

Low voltage (wetted sponge) – coatings that are less than 20 mils thick

High voltage (spark tester) – coatings that are greater than 20 mils thick

Move wand/electrode maximum of one foot/second

Inspecting OAP Coating Systems “Visual” pinhole/holiday

detection Optically Active Pigments

(OAP) added to coatings during formulation

Inspection performed using UVA-340 light

Process described in SSPC TU 11

Inspector training recommended if inspections not previously performed

Assessing Coating Drying/Cure• Pencil Hardness (ASTM D3363)• Solvent Resistance (Solvent Rubs; ASTM D5402) for

convertible coatings• Solvent Resistance (Solvent Rubs; ASTM D4752) for

ethyl silicate inorganic zinc primers• Impressor Hardness

Barcol Hardness (ASTM D2583)Durometer Hardness (ASTM D2240)

• Dry Time Testing (ASTM D1640)

Measuring Adhesion

• Adhesion is destructive testing

• Testing should not be conducted unless required

• Types of coating adhesion:The adhesion of the coating to the substrateThe adhesion of the coating layers to each otherThe inner-strength of each coating layer (cohesion)

Adhesion Test MethodsStandardStandard TitleTitle

D 3359 AD 3359 A Adhesion by Tape Test (>5 mils DFT)Adhesion by Tape Test (>5 mils DFT)

D 3359 BD 3359 B Adhesion by Tape Test (≤5 mils DFT)Adhesion by Tape Test (≤5 mils DFT)

D 6677D 6677 Knife AdhesionKnife Adhesion

D 4541D 4541

D 7234D 7234

Pull-off Strength of Coatings Using Portable Pull-off Strength of Coatings Using Portable Adhesion TestersAdhesion Testers

Pull-off Strength of Coatings on Pull-off Strength of Coatings on Concrete Concrete Using Portable Adhesion TestersUsing Portable Adhesion Testers

Tape Adhesion (D 3359) Method “A” (> 5 mils)

APPLY TAPE AND RUB ONTO SURFACE

REMOVE TAPE QUICKLY

SCRIBE AN “X” INTO COATING TO SUBSTRATE

Tape Adhesion (D 3359) Method “A” (> 5 mils)

Rating Description

5A No peeling or removal

4A Trace peeling or removal along the incisions

3A Jagged removal along the incisions up to 1/16” on either side

2A Jagged removal along the incisions up to 1/8” on either side

1A Removal of most of the coating from the area of the “X” under the tape

0A Removal of coating beyond the area of the “X”

Tape Adhesion (D 3359) Method “B” (< 5 mils)

APPLY TAPE AND RUB ONTO SURFACE

REMOVE TAPE QUICKLY

SCRIBE A CROSS-CUT PATTERN INTO COATING TO SUBSTRATE

Tape Adhesion (D 3359) Method “B” (< 5 mils)Ratin

g% Description

5B 0% Edges of cuts completely smooth

4B <5% Small flakes of coating detached at intersections

3B 6-15%

Small flakes of coating detached along edges & at intersections

2B 16-35%

Coating flaked along edges and parts of squares

1B 36-65%

Coating flaked along edges in large ribbons and whole squares detached

0B >65%

Flaking & detaching worse than 1B

Tensile (pull-off) Adhesion Testing ASTM D 4541 measures the

resistance to a perpendicular pull

Requires the attachment of “loading fixtures”

Pulling mechanisms include:SpringPneumaticHydraulic (shown)

Record psi (Mpa) and location of break

Illustrations of Various Locations of Illustrations of Various Locations of BreakBreak 1

2 3 4 5

Identifying Coating Application Defects• Multitude of defect types

• Identifying type, causes and remedies is challenging

• Acquire a pictorial reference guide

• Sources: ASTM standards Fitz’s Atlas 2™ (shown)

Summary• During this webinar, we have described :

Industry standards for coating applicationDeveloping a quality control plan for paintingNavigating a Technical (Product) Data SheetMeasuring ambient conditions and surface temperatureWitnessing mixing, thinning and application proceduresCalculating and measuring wet film thicknessDry film thickness measurementPost-application testing Identifying application defects

Quality Control of Industrial Painting Operations

William D. CorbettKTA-Tator, Inc.

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