1. Removing Coatings and Cleaning Masonry Substrates
Kenneth A. Trimber
KTA-Tator, Inc.

2. Removing Coatings and Cleaning Masonry Substrates- Webinar Learning Objectives
Identify SSPC/NACE, ASTM, and ICRI standards and guidelines applicable to cleaning and the removal of paint from CMU and brick substrates
Describe various methods of paint removal and cleaning, including advantages and disadvantages of each

3. Questions to Ask During Project Design
The following questions help to identify candidate coating cleaning or paint 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?

4. 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?

5. Industry Standards and Guides

6. Industry Standards and Guides (SSPC)
SSPC-SP13/NACE No. 6, Surface Preparation of Concrete
More of a Guide than a Standard
Frequently references other SSPC and ASTM Standards
Describes cleaning methods from air blow down and vacuum cleaning to power tool cleaning, water jetting and abrasive blast cleaning
Standard will be revised in a joint effort between the SSPC Surface Preparation Committee and the SSPC Commercial Coatings Committee

7. Industry Standards and Guides (SSPC)
SSPC-SP12/NACE No. 5, Surface Preparation and Cleaning of Metals by Water Jetting Prior to Recoating – replaced with:
SSPC-SP WJ-4/NACE WJ-4, Waterjet Cleaning of Metals – Light Cleaning
SSPC-SP WJ-3/NACE WJ-3, Waterjet Cleaning of Metals – Thorough Cleaning
SSPC-SP WJ-2/NACE WJ-2, Waterjet Cleaning of Metals – Very Thorough Cleaning
SSPC-SP WJ-1/NACE WJ-1, Waterjet Cleaning of Metals – Clean to Bare Substrate

8. SSPC Visual Guides for Surface Cleanliness – Steel (not Concrete)
SSPC Visual Reference Photographs are well established for the cleaning of steel, but none exist for the cleaning of concrete
The SSPC Commercial Coatings Committee will be filling this void and developing reference photographs for the preparation of concrete-both cleanliness and roughness

9. Industry Standards and Guides (ICRI)
ICRI Guideline No (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays
Addresses water and detergent cleaning, acid etching, a variety of power tool methods, abrasive blast cleaning, and flame blasting
ICRI – 9 Concrete Surface Profile (CSP) Coupons

10. Industry Standards and Guides (ASTM)
ASTM D4258, Surface Cleaning Concrete for Coating
Broom cleaning, vacuum cleaning, air blast cleaning, water cleaning, detergent cleaning, steam cleaning
ASTM D4259, Abrading Concrete
Power tool, water blast, and wet/dry abrasive blast cleaning
ASTM D4260, Liquid and Gelled Acid Etching of Concrete
ASTM D4261, Surface Cleaning Concrete Masonry Units for Coating
Same as D4269 with the addition of mechanical tool cleaning for the removal of mortar spatter and efflorescence

11. Surface Preparation/Cleaning Methods in Standards/Guides
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
Chemical Stripping
Effective method of paint removal, but not addressed in the standards/guides

12. Surface Preparation/Cleaning Methods in Standards/Guides (con’t)
Acid Etching
SSPC-SP13/NACE No. 6
ICRI Guideline No
ASTM D4260
Flame Cleaning
Power Grinding/Sanding
ASTM D4259

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

14. Surface Preparation/Cleaning Methods in Standards/Guides (con’t)
Wet Abrasive Blast Cleaning
SSPC-SP13/NACE No. 6
ASTM D4259
Dry Abrasive Blast Cleaning
ICRI Guideline No

15. 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

16. Dry Abrasive Blast Cleaning
Abrasives propelled by compressed air
Very dusty – typically requires containment system

17. Dry Abrasive Blast Cleaning
Boiler slag, copper slag, nickel slag, garnet, crushed glass, sponge, walnut shells, others

18. 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, especially when trying to remove all coating

19. 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

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

21. Wet Abrasive Blast Cleaning (con’t)

22. Sodium Bicarbonate Blast Cleaning
Variation of wet or dry 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

23. Sodium Bicarbonate Blast Cleaning – efflorescence (wet)

24. Sodium Bicarbonate Blast Cleaning – fire restoration (dry)

25. Water Cleaning Low Pressure <5,000 psi High Pressure 5,000 to 10,000 psi
Pressure categories defined in
SSPC-SP WJ-4/NACE WJ-4
SSPC-SP WJ-3/NACE WJ-3
SSPC-SP WJ-2/NACE WJ-2
SSPC-SP WJ-1/NACE WJ-1
Despite the titles, the methods are suitable for CMU/brick

26. 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

27. 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

28. Water Cleaning (con’t) Low Pressure <5,000 psi High Pressure 5,000 to 10,000 psi
When used for surface cleaning, operator discipline is required to assure the complete cleaning is achieved

29. 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 softens paint during removal

30. High Temperature Low Pressure Water Cleaning (<5,000 psi) - con’t

31. Water Jetting High Pressure 10,000 to 30,000 psi Ultra -High Pressure >30,000 psi
Typically less water volume than low pressure cleaning methods
Efficiently removes existing coating, but can roughen substrate

32. 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

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

34. Power Tool Cleaning
Power sanding, power grinding, needle gunning, rotopeening
Vacuum shrouding available

35. Power Tool Cleaning
Sanding and grinding remove paint with less damage to substrate than impact methods

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

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

38. 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

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

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

41. Chemical Stripping
Second application essentially removes all coating

42. 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?

43. Practical Use of Candidate Surface Preparation Methods
Paint Removal Methods1
Extent of Coating Removal Feasible
Substrate Roughening
Extent of Paint or Residue in Porosity
Volume of Water Used
Quantity of Airborne Dust
Generated
Partial
Total
Slight to none
Heavy
Slight
Mod
Large
Little
Much
Dry abrasive blast x
none
Wet abrasive blast
Sodium bicarb blast x2
Pressure water (<10k)
High temp water (<5k)
Water jetting (>10k) x3
Power tool cleaning
x 4
Chemical stripping x5
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, and low pressure water (5k) can remove all coating, but they are not commonly used in these ways.
2 – Sodium bicarbonate is best suited for surface cleaning rather than paint removal. It can be used wet or dry. If used dry, a large quantity of airborne dust is created. When used wet, little to no dust is generated.
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 – Roughening created by power tool cleaning is dependent on the tool being used, ranging from slight to no roughening with power sanding to heavy roughening with power impact tools.
5 – 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 to flush the surface, but this is only practical for small localized areas.

44. 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 ( )

45. Additional Information
A paper associated with the information in this webinar was published in Durability + Design Magazine – March/April 2011
Sources of equipment and materials can be found in the Durability + Design on-line Painting Equipment and Supplies Buying Guide (under the Buying Guides tab on the home page)

46. Removing Coatings and Cleaning Masonry Substrates - Questions
Kenneth Trimber ,x204