Presentation on theme: "Removing Coatings and Cleaning Masonry Substrates"— Presentation transcript:
1Removing Coatings and Cleaning Masonry Substrates Kenneth A. TrimberKTA-Tator, Inc.
2Removing 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 substratesDescribe various methods of paint removal and cleaning, including advantages and disadvantages of each
3Questions 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?
4Questions 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?
6Industry Standards and Guides (SSPC) SSPC-SP13/NACE No. 6, Surface Preparation of ConcreteMore of a Guide than a StandardFrequently references other SSPC and ASTM StandardsDescribes cleaning methods from air blow down and vacuum cleaning to power tool cleaning, water jetting and abrasive blast cleaningStandard will be revised in a joint effort between the SSPC Surface Preparation Committee and the SSPC Commercial Coatings Committee
7Industry 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 CleaningSSPC-SP WJ-3/NACE WJ-3, Waterjet Cleaning of Metals – Thorough CleaningSSPC-SP WJ-2/NACE WJ-2, Waterjet Cleaning of Metals – Very Thorough CleaningSSPC-SP WJ-1/NACE WJ-1, Waterjet Cleaning of Metals – Clean to Bare Substrate
8SSPC 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 concreteThe SSPC Commercial Coatings Committee will be filling this void and developing reference photographs for the preparation of concrete-both cleanliness and roughness
9Industry Standards and Guides (ICRI) ICRI Guideline No (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer OverlaysAddresses water and detergent cleaning, acid etching, a variety of power tool methods, abrasive blast cleaning, and flame blastingICRI – 9 Concrete Surface Profile (CSP) Coupons
10Industry Standards and Guides (ASTM) ASTM D4258, Surface Cleaning Concrete for CoatingBroom cleaning, vacuum cleaning, air blast cleaning, water cleaning, detergent cleaning, steam cleaningASTM D4259, Abrading ConcretePower tool, water blast, and wet/dry abrasive blast cleaningASTM D4260, Liquid and Gelled Acid Etching of ConcreteASTM D4261, Surface Cleaning Concrete Masonry Units for CoatingSame as D4269 with the addition of mechanical tool cleaning for the removal of mortar spatter and efflorescence
11Surface Preparation/Cleaning Methods in Standards/Guides Detergent CleaningSSPC-SP13/NACE No. 6ICRI Guideline NoASTM D4258, ASTM D4261Air Blast Cleaning, Water Cleaning, Steam Cleaning, Vacuum CleaningSSPC-SP13/NACE 6Chemical StrippingEffective method of paint removal, but not addressed in the standards/guides
18Dry Abrasive Blast Cleaning (con’t) Difficult to selectively remove loose coatingElastomeric coatings can be difficult to remove due to bounce back of the abrasivePotential for very heavy roughening of the substrate and damage to mortar joints, especially when trying to remove all coating
19Wet Abrasive Blast Cleaning Variation of dry abrasive blast cleaningWater is mixed with the abrasive to control dustingSame potential to roughen the substrate as dry abrasive blast cleaning
20Wet Abrasive Blast Cleaning (con’t) Expendable abrasive, same as dry blast cleaningWater is mixed with abrasive using:Water collarSpecial injection nozzleSpecial equipment that creates a slurry
22Sodium Bicarbonate Blast Cleaning Variation of wet or dry abrasive blast cleaningSodium bicarbonate (baking soda) is the abrasiveLarger particle size than household baking sodaGood for removing surface contamination, graffiti, and efflorescence
24Sodium Bicarbonate Blast Cleaning – fire restoration (dry)
25Water Cleaning Low Pressure <5,000 psi High Pressure 5,000 to 10,000 psi Pressure categories defined inSSPC-SP WJ-4/NACE WJ-4SSPC-SP WJ-3/NACE WJ-3SSPC-SP WJ-2/NACE WJ-2SSPC-SP WJ-1/NACE WJ-1Despite the titles, the methods are suitable for CMU/brick
26Water Cleaning (con’t) Low Pressure <5,000 psi High Pressure 5,000 to 10,000 psi Will effectively remove loose coatingZero degree rotating tip improves efficiencyCan remove all coating given ample dwell timeGenerally 5.0 to 10.0 gal/min
27Water 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 removalIncreased dwell time for total removal can lead to water intrusion and wetting of interior surfaces
28Water 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
29High Temperature Low Pressure Water Cleaning (<5,000 psi) Water temperature 250ºF and pressures <5,000 psiHigh temperature improves cleaning efficiency when removing all coatingHigh temperature softens paint during removal
30High Temperature Low Pressure Water Cleaning (<5,000 psi) - con’t
31Water Jetting High Pressure 10,000 to 30,000 psi Ultra -High Pressure >30,000 psi Typically less water volume than low pressure cleaning methodsEfficiently removes existing coating, but can roughen substrate
32Water 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
33Water Jetting (con’t) High Pressure 10,000 to 30,000 psi Ultra -High Pressure >30,000 psi
34Power Tool CleaningPower sanding, power grinding, needle gunning, rotopeeningVacuum shrouding available
35Power Tool CleaningSanding and grinding remove paint with less damage to substrate than impact methods
36Power Tool Cleaning (con’t) Power tool cleaning best used for localized removalSanding methods good for feathering
37Chemical StrippingChemical stripping effectively removes existing paintBiodegradable strippers are available that do not contain methylene chloride or caustic materials
38Chemical Stripping – con’t Stripper is first applied to the surface by brush, roller, or sprayDwell time depends on coating type, temperature and thickness, but typically overnight
39Chemical Stripping – con’t Stripper and coating are removed by scraping, bucket and sponge, or pressure washing
40Chemical Stripping – con’t Depending on results, a second application may be necessary
41Chemical StrippingSecond application essentially removes all coating
42Original 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?
43Practical Use of Candidate Surface Preparation Methods Paint Removal Methods1Extent of Coating Removal FeasibleSubstrate RougheningExtent of Paint or Residue in PorosityVolume of Water UsedQuantity of Airborne DustGeneratedPartialTotalSlight to noneHeavySlightModLargeLittleMuchDry abrasive blastxnoneWet abrasive blastSodium bicarb blastx2Pressure water (<10k)High temp water (<5k)Water jetting (>10k)x3Power tool cleaningx 4Chemical strippingx51 – 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.
44Productivity 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 ( )
45Additional Information A paper associated with the information in this webinar was published in Durability + Design Magazine – March/April 2011Sources 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)