Paint Removal from CMU and Brick Kenneth A. Trimber KTA-Tator, Inc.

Paint Removal from CMU and Brick - Webinar Learning Objectives  Identify SSPC/NACE, ASTM, and ICRI standards and guidelines applicable to the removal of paint from CMU and brick substrates  Describe various methods of paint removal, including advantages and disadvantages of each

Questions to Ask During Project Design The following questions help to identify candidate coating removal methods for the project: Does all coating have to be removed, or just loose coating? If all coating must be removed, can small amounts still be permitted to remain in the porosity of the block? 3

Questions to Ask During Project Design (con’t) Can roughening of the block or brick be tolerated. If so, can it be heavy or only slight? Can large volumes of water be tolerated (environmentally and in terms of potential water intrusion into the substrate)? Can airborne dust be tolerated? 4

Industry Standards and Guides 5

Industry Standards and Guides (con’t) SSPC-SP13/NACE No. 6, Surface Preparation of Concrete SSPC-SP12/NACE No. 5, Surface Preparation and Cleaning of Metals by Water Jetting Prior to Recoating ICRI Guideline No (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays 6

ICRI – 9 Concrete Surface Profile (CSP) Coupons 7

Industry Standards and Guides (con’t) ASTM Standard Practices –ASTM D4258, Surface Cleaning Concrete for Coating –ASTM D4259, Abrading Concrete –ASTM D4260, Liquid and Gelled Acid Etching of Concrete –ASTM D4261, Surface Cleaning Concrete Masonry Units for Coating 8

Surface Preparation/Cleaning Methods in Standards/Guides Dry Abrasive Blast Cleaning –SSPC-SP13/NACE No. 6 –ICRI Guideline No –ASTM D4259 Water Cleaning/Water Jetting –SSPC-SP13/NACE No. 6 –ICRI Guideline No –ASTM D4259 Wet Abrasive Blast Cleaning –SSPC-SP13/NACE No. 6 –ASTM D4259 9

Surface Preparation/Cleaning Methods in Standards/Guides (con’t) Impact Power Tool Cleaning –SSPC-SP13/NACE No. 6 –ICRI Guideline No –ASTM D4259 Power Grinding/Sanding –SSPC-SP13/NACE No. 6 –ICRI Guideline No –ASTM D4259 Scarifying/Grinding/Scabbling/Milling –ICRI Guideline No –ASTM D

Surface Preparation/Cleaning Methods in Standards/Guides (con’t) Acid Etching –SSPC-SP13/NACE No. 6 –ICRI Guideline No –ASTM D4260 Flame Cleaning –SSPC-SP13/NACE No. 6 –ICRI Guideline No

Surface Preparation/Cleaning Methods in Standards/Guides (con’t) Detergent Cleaning –SSPC-SP13/NACE No. 6 –ICRI Guideline No –ASTM D4258, ASTM D4261 Air Blast Cleaning, Water Cleaning, Steam Cleaning, Vacuum Cleaning –SSPC-SP13/NACE 6 –ASTM D4258, ASTM D4261 Chemical Stripping –Effective method of paint removal, but not addressed in the standards/guides 12

Candidate Paint Removal Methods for CMU/Brick Dry Abrasive Blast Cleaning Wet Abrasive Blast Cleaning Sodium Bicarbonate Blast Cleaning Water Cleaning (Low Pressure <5,000 psi; High Pressure ,000 psi) High Temperature Pressure Water Cleaning (<5,000 psi) Water Jetting (High Pressure 10,000 – 30,000 psi; Ultra- High Pressure (>30,000 psi) Power Tool Cleaning Chemical Stripping 13

Dry Abrasive Blast Cleaning  Abrasives propelled by compressed air  Boiler slag, copper slag, nickel slag, garnet, crushed glass, sponge, walnut shells, others  Very dusty – may require containment system

Dry Abrasive Blast Cleaning (con’t)  Difficult to selectively remove loose coating  Elastomeric coatings can be difficult to remove due to bounce back of the abrasive  Potential for very heavy roughening of the substrate and damage to mortar joints

Wet Abrasive Blast Cleaning  Variation of dry abrasive blast cleaning  Water is mixed with the abrasive to control dusting  Same potential to roughen the substrate as dry abrasive blast cleaning

Wet Abrasive Blast Cleaning (con’t)  Expendable abrasive, same as dry blast cleaning  Water is mixed with abrasive using: –Water collar –Special nozzle –Special equipment that creates a slurry

Sodium Bicarbonate Blast Cleaning  Variation of wet abrasive blast cleaning  Sodium bicarbonate (baking soda) is the abrasive  Larger particle size than household baking soda  Good for removing surface contamination, graffiti, and efflorescence

Water Cleaning Low Pressure <5,000 psi High Pressure 5,000 to 10,000 psi  Pressure categories defined in SSPC-SP12/ NACE No. 5, Surface Preparation and Cleaning of Metals by Water Jetting Prior to Recoating  Despite the title, the methods suitable for CMU/brick

Water Cleaning (con’t) Low Pressure <5,000 psi High Pressure 5,000 to 10,000 psi  Will effectively remove loose coating  Zero degree rotating tip improves efficiency  Can remove all coating given ample dwell time  Generally 5.0 to 10.0 gal/min

Water Cleaning ( con’t) Low Pressure <5,000 psi High Pressure 5,000 to 10,000 psi  Potential for using large amount of water, especially for total coating removal  Increased dwell time for total removal can lead to water intrusion and wetting of interior surfaces

High Temperature Low Pressure Water Cleaning (<5,000 psi)  Water temperature 250ºF and pressures <5,000 psi  High temperature improves cleaning efficiency when removing all coating.

High Temperature Low Pressure Water Cleaning (<5,000 psi) - con’t  High temperature softens paint during removal

Water Jetting High Pressure 10,000 to 30,000 psi Ultra -High Pressure >30,000 psi  SSPC-SP12/NACE No. 5  Typically less water volume than low pressure cleaning methods  Efficiently removes existing coating

Water Jetting (con’t) High Pressure 10,000 to 30,000 psi Ultra -High Pressure >30,000 psi  Integral vacuum recovery system improves housekeeping and cleanup

Water Jetting ( con’t) High Pressure 10,000 to 30,000 psi Ultra -High Pressure >30,000 psi

Power Tool Cleaning  Power sanding, power grinding, needle gunning, rotopeening  Sanding and grinding remove paint with less damage to substrate than impact methods  Vacuum shrouding available

Power Tool Cleaning (con’t)  Power tool cleaning best used for localized removal  Sanding methods good for feathering

Chemical Stripping  Chemical stripping effectively removes existing paint  Biodegradable strippers are available that do not contain methylene chloride or caustic materials

Chemical Stripping – con’t  Stripper is first applied to the surface by brush, roller, or spray  Dwell time depends on coating type, temperature and thickness, but typically overnight

Chemical Stripping – con’t  Stripper and coating are removed by scraping, bucket and sponge, or pressure washing

Chemical Stripping – con’t  Depending on results, a second application may be necessary

Chemical Stripping  Second application essentially removes all coating

Original Project Design Questions Does all coating have to be removed, or just loose coating? If all coating must be removed, can small amounts still be permitted to remain in the porosity of the block? Can roughening of the block or brick be tolerated. If so, can it be heavy or only slight? Can large volumes of water be tolerated (environmentally and in terms of potential water intrusion into the substrate)? Can airborne dust be tolerated? 34

Practical Use of Candidate Surface Preparation Methods 35 1 – This table represents the practical application of the various methods when used under normal operations, but it is not absolute. For example, abrasive blast cleaning can partially remove existing coating from CMU or brick, but it is not commonly used for this purpose. 2 – Roughening created by power tool cleaning is dependent on the tool being used, ranging from slight roughening with power sanding to heavy roughening with power impact tools. 3 - Slight to heavy roughening may occur. Vacuum shrouding will significantly reduce the volume of water. Without vacuum shrouding, the volume is greater, but typically not as high as pressure washing at < 10,000 psi. 4 – A large volume of water is generated if the stripper is removed by pressure washing. Much less water is involved if removed by scraping and sponge/water, but this is only practical for small localized areas. Paint Removal MethodsExtent of Coating Removal Feasible Substrate Roughening Extent of Paint Residue in Porosity Volume of Water Used Quantity of Airborne Dust Generated PartialTotalSlight to none HeavySlightMod LargeLittleMuch Dry abrasive blastxxxnonex Wet abrasive blastxxxxx Sodium bicarb blastxxxxnone Pressure water (<10k)xxxxnone High temp water (<5k)xxxxxnone Water jetting (>10k)xxx3x3 x3x3 xx3x3 x3x3 none Power tool cleaningx x 2 xnonex Chemical strippingxxxx4x4 x4x4 none

Practical Use of Candidate Surface Preparation Methods 36. Paint Removal MethodsExtent of Coating Removal Feasible PartialTotal Dry abrasive blastx Wet abrasive blastx Sodium bicarbonate blastx Pressure water (<10k)x High temp water (<5k)xx Water jetting (>10k)xx Power tool cleaningx Chemical strippingx

Practical Use of Candidate Surface Preparation Methods 37 2 – Roughening created by power tool cleaning is dependent on the tool being used, ranging from slight roughening with power sanding to heavy roughening with power impact tools. 3 – Slight to heavy roughening may occur Paint Removal MethodsSubstrate Roughening Slight to none Heavy Dry abrasive blastx Wet abrasive blastx Sodium bicarbonate blastx Pressure water (<10k)x High temp water (<5k)x Water jetting (>10k)x3x3 x3x3 Power tool cleaning x 2 Chemical strippingx

Practical Use of Candidate Surface Preparation Methods 38 Paint Removal MethodsExtent of Paint Residue in Porosity SlightMod Dry abrasive blastx Wet abrasive blastx Sodium bicarbonate blastx Pressure water (<10k)x High temp water (<5k)x Water jetting (>10k)x Power tool cleaningx Chemical strippingx

Practical Use of Candidate Surface Preparation Methods 39 3 – Vacuum shrouding will significantly reduce the volume of water. Without vacuum shrouding, the volume is greater, but typically not as high as pressure washing at < 10,000 psi. 4 – A large volume of water is generated if the stripper is removed by pressure washing. Much less water is involved if removed by scraping and sponge/water, but this is only practical for small localized areas. Paint Removal MethodsVolume of Water Used ModLarge Dry abrasive blastnone Wet abrasive blastx Sodium bicarbonate blastx Pressure water (<10k)x High temp water (<5k)x Water jetting (>10k)x3x3 x3x3 Power tool cleaningnone Chemical strippingx4x4 x4x4

Practical Use of Candidate Surface Preparation Methods 40 Paint Removal MethodsQuantity of Airborne Dust Generated LittleMuch Dry abrasive blastx Wet abrasive blastx Sodium bicarbonate blastnone Pressure water (<10k)none High temp water (<5k)none Water jetting (>10k)none Power tool cleaningx Chemical strippingnone

Productivity Production rates for some of the methods can be found in: –Painting and Decorating Contractors of America (PDCA) Estimating Guide, Volume 2, Rates and Tables ( ) –ICRI Guideline No (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays ( ) 41

Additional Information Paper associated with the webinar to be published in Durability + Design daily e- news - week of November 1, 2010 SSPC 2011 – One day seminar on commercial painting – problems with painting CMU, surface preparation, application, and paint systems Feb 1,

Paint Removal from Masonry Substrates Webinar - Questions