Surface Preparation and Overcoating of Factory-

Applied Finishes

James D. MachenKTA-Tator, Inc.

Surface Preparation and Overcoating of Factory-Applied Finishes –

Overview of Presentation Objectives…

1. Where and why factory finishes are used

2. Generic types of factory finishes

3. How to assess the physical condition of a factory finish to determine overcoat viability

Webinar Learning Objectives (con’t)

4. How to prepare a factory finish for overcoating

5. How to identify candidate overcoat materials

6. Use of coatings test patch to validate surface preparation and overcoat options

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Uses for Factory-Applied Finishes

• Standing Seam Roof Panels

• Building Facade Panels

• Canopies• Awnings• Curtain Walls• Railings• Window

Frames/Mullions

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• Other Decorative Architectural Metal

Metal Substrates to which Factory Finishes are Applied

• Galvanized sheet metal– zinc or zinc/aluminum (trade names such as Gavalume®, Zincalume®)

• Aluminum sheet metal• Aluminum extrusions

Sheet metal is typically supplied in “coils” that are coated in a “coil coating” process.

Extrusions are typically coated by spray application.

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Generic Types of Factory Finishes

• Fluoropolymers • Polyesters• Silicone modified polyesters• Acrylics

50% to 70% fluoropolymer (PVDF) formulations are typically superior.

Performance qualities of factory finishes are enhanced by post baking.

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Common Factory-Applied Finishes

• ASTM A755/A755M – 11, Standard Specification for Steel Sheet, Metallic Coated by the Hot-Dip Process and Prepainted by the Coil-Coating Process for Exterior Exposed Building Products

– Exposed side – polyester, silicone polyester, acrylic, fluoropolymer, plastisol, polyurethane

– Interior (protected side) – polyester, acrylic

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Common Factory-Applied Finishes (cont.)

• AAMA (Architectural Aluminum Metal Manufacturers Association) 2603, Voluntary Specification, Performance Requirements and Test Procedures for Pigmented Organic Coatings on Aluminum Extrusions and Panels

– Least rigorous of the 3 AAMA standards– 1 year South Florida Exposure– Good level of performance and general appearance –

typically interior exposure– Baked polyester and acrylic

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Common Factory-Applied Finishes (cont.)

• AAMA (Architectural Aluminum Metal Manufacturers Association) 2604, Voluntary Specification, Performance Requirements and Test Procedures for High Performance Organic Coatings on Aluminum Extrusions and Panels

– Middle of the 3 AAMA standards– 5 years South Florida Exposure– High level of performance and general appearance – Silicone-modified polyester and 50% polyvinylidene

fluoride (PVDF)

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Common Factory-Applied Finishes (cont.)

• AAMA (Architectural Aluminum Metal Manufacturers Association) 2605, Voluntary Specification, Performance Requirements and Test Procedures for Superior Performing Organic Coatings on Aluminum Extrusions and Panels

– Most rigorous of the 3 AAMA standards– 10 years South Florida Exposure– Superior level of performance and general appearance – 70% polyvinylidene fluoride (PVDF)

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Benefits of Factory-Applied Finishes

Factory Finishes Provide Excellent……..

• Weathering characteristics

• Color and gloss retention

• Corrosion protection

• Automotive-like finish

• Long term performance

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Manufacture Warranties

• 10 and 20 year warranties depending on local exposure conditions:

– Intensity of UV exposure– Airborne pollutants– Chloride, seacoast exposure– Time of wetness– Installation Orientation (vertical vs. low angle)

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Warranties Cover

• Peeling• Gloss reduction

greater than X• Color shift

greater than Y

NOTE: Warranties for exterior exposure do not claim that color and gloss will not shift, but that the shift will be less than a certain amount compared to original baseline measurements.

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Maintenance of Factory Finishes Maintain as long as possible by……

• Periodic detergent washing and cleaning

• Cleaning every 6 months prevents build up of chloride and acid salts

• Cleaning removes debris that increases time of wetness

• Clean mildew and fungal growth at same time (1 gallon household bleach, cup of soap, 5 gallons water)

Use Repainting as Last Resort

• Painting introduces risk of peeling…..– New coating to factory

finish– Between factory finish and

substrate

• Field-applied coating will not have the same automotive look

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• Systematic steps for assessing the condition, preparing the surface and overcoating factory finishes are required.

Systematic Approach of Assessing Factory Finishes for Overcoating

Steps Consist of…….

STEP 1 – Determining the Generic Type of Existing Finish

STEP 2 – Assessing the Condition of the Factory Finish

STEP 3 – Preparing the Factory Finish for Overcoating

STEP 4 – Choosing Candidate Overcoat Materials

STEP 5 – Performing a Coatings Test Patch

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STEP 1 – Determine the Generic Coating Type of

Existing FinishMake Determinations By…….

• Reviewing original specification or project procurement documents– Be aware of alternate or substitute products

• Manufacturer’s warranty documents may identify material suppliers or manufacturers, product trade names or the shop applicator– Shops oftentimes use sole source of supply

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STEP 1 – Determine the Generic Coating Type of Existing Finish

(cont.)

If all else fails…• Laboratory Analysis to identify generic type

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Infrared Spectroscopy

STEP 2 – Assess the Condition of the Factory Finish

Involves a series of sub-steps to determine the suitability of the existing factory finish for overcoating.

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• Visual Assessment- Lifting, Peeling- Rusting (use SSPC-VIS 2

pictorial standard to characterize and quantify rust)

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STEP 2 – Assess the Condition of the Factory Finish (cont.)

• Paint Thickness- Determine representative

thickness range

– ASTM D 33359 – Measuring Adhesion by Tape Test

– ASTM D 6677 – Standard Test Method for evaluating Adhesion by Knife Test

– ASTM D 4541 – Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers

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STEP 2 – Assess the Condition of the Factory Finish (cont.)

• Adhesion – A “sound foundation” for overcoating

Knowing the Physical Characteristics of the Existing Coating Helps to determine Associated Risk Level

• Guidance typically provided by the overcoat material manufacturer

• Other industry publications and documents

– SSPC-TU 3, Overcoating

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STEP 2 – Assess the Condition of the Factory Finish (cont.)

STEP 3 – Prepare the Factory Finish for Overcoating

• Hand and/or Power Tool Cleaning– SSPC-SP 2 or SP 3 to

remove loose deteriorated coating or metal oxidation (corrosion)

– Feather-edge transition (dull putty knife test)

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Used to review candidate methods of surface preparation

• Pay attention to…..

- Field cut edges

- Field formed surfaces (tooling damage)

- High foot traffic areas

- Ice damage areas

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STEP 3 – Prepare the Factory Finish for Overcoating (cont.)

• Overall Surface Cleaning– Remove dirt/grime/oil/other contaminants by

pressurized water cleaning

– Fan angle of pressurized water – 0, 15, 25

– Be careful not to damage intact coating or substrate with pressurized water

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STEP 3 – Prepare the Factory Finish for Overcoating (cont.)

• Brush-off Blast Clean– Control process – lower air pressures, use

fine/soft abrasives, increase stand-off distances26

STEP 3 – Prepare the Factory Finish for Overcoating (cont.)

• Surface Roughening- Superficial roughening

only, no coating or substrate damage

- Dull gloss/sheen

• Sanding- Use fine grade of

sandpaper

• Use Less Aggressive Abrasive Media or Methods

– Urethane foam sponge, walnut shells, crushed glass, fine garnet, other hybrid mixtures

– New low impact technologies utilizing water vapor and low operating pressures

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STEP 3 – Prepare the Factory Finish for Overcoating (cont.)

• Goal of Surface Roughening …..

– Provide a uniform and dense surface roughness in a continuous pattern of peaks and valleys with no smooth, un-profiled areas.

– Not damage the intact coatings or the underlying substrate

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STEP 3 – Prepare the Factory Finish for Overcoating (cont.)

STEP 4 – Choose Candidate Overcoat Materials

Candidate Overcoat Materials Qualities…..

• Compatible with existing factory finish

• Field application friendly

• Good adhesion characteristics

• Suitable for the intended exposure environment• Capable of producing the desired finish

appearance

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• Compatibility with Existing Factory Finish is best determined by……

– Proven history of performance• Air drying fluoropolymers (FEVE)• Advanced acrylic formulations

or……

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STEP 4 – Choose Candidate Overcoat Materials (cont.)

STEP 5 – Candidate Coating Test Patches

• Confirms and validates information obtained from previous steps.

• May include evaluation of multiple surface preparation and coating types

• ASTM D5064, Standard Practice for Conducting a Patch Test to Access Coating Compatibility

• Test Patch Exposure Time– Minimum – after full manufacturer curing intervals– Optimal – 6 mos. to 1 year – cyclic weathering– Generally, the longer the exposure time, the more useful

the information for predicting risk

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In conclusion, key steps include…1. Determining the type of the existing finish2. Assessing the physical characteristics of the

existing finish3. Reviewing candidate surface preparation

methods4. Reviewing candidate overcoating materials5. Incorporating information obtained in Steps 1

through 4 into a Coatings Test Patch Program

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Conclusion

Make an Informed Decision

The above steps provide valuable information for an informed decision.

Process requires…• Initial expenditure of

– Time– Money– Manpower

• Minimizes “guess” work of overcoating

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Surface Preparation and Overcoating of Factory Applied

Finishes

Questions?