INTRODUCTION This article is presented in three parts. Part I, published in March, provided an analysis of types of paints and coatings. In Part II, published in June, surface preparation and application were discussed. This, Part III of the series, will conclude the discussion on recommended coating systems and application procedures for a coastal environment. APPLICATION If the coating is not applied properly by skilled applicators, all the efforts in selecting the coating and preparing the surfaces are wasted. Successful application includes the following: • Proper tools. • Proper curing. • Back priming. • Proper thickness. • Stripe inside outside corners, welds. • Proper conditions (temperature, humidity, moisture, wind). • Proper training and familiarity with the coatings to be applied. TOOLS The most frequently used tools are brushes, rollers, and sprays. Since each method produces different coating thicknesses and finishes, except for extenuating circumstances, the methods should not be mixed on the same surface. Brushes Brushes allow for the most control of coating application with the least amount of waste and mess. A brush usually produces the thinnest film build per coat. Actually, it may be difficult to achieve the listed wetfilm thickness per coat with a brush, especially if a high-build coating is being applied. The same type of brush cannot be used for all coatings, and the manufacturer’s recommendations for brushes should be followed. Always select the type of brush recommended (natural bristle, synthetic bristle, etc.) and of the best quality, as the difference in brush quality can easily be seen and felt. Premium quality brushes can be cleaned repeatedly, while economy brushes are considered disposable. Brushes tend to leave stroke marks and streaks and are more likely to leave thin spots or “holidays.” However, premium brushes tend to leave fewer noticeable marks. When doing furniture refinishing, premium brushes were used to apply varnishes, and when the brushes were no longer suitable for varnish, they were relegated to painting. Rollers Rollers allow the coating to cover a larger area faster and the application of the coating to a thicker film build than a brush. Normally, coatings formulated for spray application can also be applied by brush or roller, but film build will be significantly less and may not be as smooth as when applied by spray. However, always ensure that the coating can be applied with a roller, as there are some coatings that are made for spray application. Usually, brushes can apply Figure 3-1 – Wood columns painted with an oil-base system and ravaged by years of weathering. The wood in the background is somewhat protected and does not seem to be experiencing the weathering as in the foreground. Photo by Nick Galizia. J U LY 2007 I N T E R FA C E • 3 3 coatings more accurately than a spray or roller. Depending on nap size and length, rollers tend to leave an orange-peel appearance, and do not cover corners well. Coatings that contain strong solvents can literally dissolve economy rollers and leave residue from the dissolved rollers in the roller pans and on surfaces. Roller covers come in different nap thicknesses that can be matched to the surface being coated and the desired finish. The longer the nap, the thicker the coating application and the greater the spatter. The usual nap thicknesses are 1/4-in, 3/8-in, 1/2-in, 3/4-in, and 1 in. Like paint brushes, roller covers come in different quality levels. The best ones can be washed repeatedly. Rollers usually apply coatings to a thicker film than brushes, but they tend to sling paint where it is not wanted, especially when a longer-nap roller is used. Shortnap rollers should be used on smooth surfaces or when a smooth finish is desired, while long-nap rollers should be used for rough surfaces or when an orange-peel effect is desired. Spray Spray is the fastest method of application and requires the most skill and proper equipment to ensure a successful result. Spraying can usually apply coatings to thicker film while producing considerable overspray and waste. Coatings applied by spray tend to be smoother but are prone to runs and sags because of the thicker application. Spraying can produce significant waste, especially when small profiles such as small diameter pipe bar joists and chainlink fences are being painted. Wind, which is common in coastal regions, can carry spray a long way and make for unhappy tourists! COSTS The following cost estimates are for comparison and include surface preparation, materials, and labor. Where finishes are field-applied, costs are based on primer being shop-applied. Costs may vary according to geographic location, applicator’s experience and capabilities, and product availability. CMU and Brick Costs include primer/filler/finish. • High-performance acrylic: +25% over unpainted CMU. • Modified epoxy, self-priming: +25% over acrylic (system is selfpriming; requires only two coats). Roofing Siding Panels Mill-finish Galvalume is base cost. • Shop-applied silicone polyester finish: +10% over mill finish. • Shop-applied Kynar, two-coat finish: +18% over mill finish. Aluminum Extrusions Mill-finish aluminum is base cost. • Shop-applied clear anodized: +26% over mill finish. • Shop-applied bronze anodized: +360% over mill finish. • Shop-applied Kynar, two-coat: +360% over mill finish. • Shop-applied powder coat, thermoset: +400% over mill finish. MATCH THE COATING SYSTEM WITH THE AMBIENT CONDITIONS AND SELECT THE BEST COATING SYSTEM THE BUDGET CAN AFFORD. 34 • I N T E R FA C E J U LY 2007 Steel, Shop-primed Fabricator’s standard shop primer at 1 – 1.5 mils DFT is base cost. • One coat of high performance alkyd at 3 mils DFT: +100%. • One coat of epoxy primer at 3 – 4 mils DFT: +150% • One coat inorganic zinc primer at 3 mils DFT: +450%. Steel, Field-coated Two coats of field-applied, standard oil paint is base cost. • Two coats of field-applied, highbuild alkyd (base cost): +25%. • Two coats of field-applied, high-performance acrylic: +50%. • One coat field-applied, epoxy polyamide and aliphatic polyurethane finish: + 80%. SUGGESTED COATING SYSTEMS FOR THE COAST DEFINITIONS The terms and commonly accepted definitions below are often encountered when coating systems are described. Substrate: The base being coated, such as wood, steel, or CMU. It is not the primer or undercoat. Coating: A thick film usually applied at approximately three mils dry film thickness (DFT). Typically has a primary purpose of protection and a secondary purpose of aesthetics. Paint: A thin film usually applied at approximately two mils DFT or less. Normally has a primary purpose of J U LY 2007 I N T E R FA C E • 3 5 Figure 3-2 – Steel framing that received inadequate surface preparation. The edges were also not stripped in during painting. Insufficient maintenance painting has taken its toll. Photo by Nick Galizia. Figure 3-3 – Steel support with epoxy primer and polyurethane finish and steel standing seam roof with fluoropolymer finish. In excellent condition after approximately seven years’ service. Figure 3-4 – Standing seam roof with fluoropolymer finish over galvanized that is showing excellent performance, color, and gloss retention after prolonged exposure. Photo by Nick Galizia. aesthetics and a secondary purpose of protection. Primer: The first coat applied to a substrate. Establishes the foundation for additional coats. Intermediate coat: First coat applied over a primer and under the finish coat. In a four-coat system, the two coats between the primer and finish coats would be intermediate coats. Finish coat: The last coat applied, directly exposed to ambient conditions. Top coat: Same as a finish coat. Undercoat: Coating between the primer and finish coat. The same as an intermediate coat in a three-coat system. Tie (barrier) coat: A coating that can Figure 3-5 – Carbon-steel supports coated with epoxy primer and polyurethane finish after approximately seven years’ service. Although the steel is under cover, salt-laden moisture can collect in crevices and on flat areas. This system should maintain its appearance for another seven-plus years. Figure 3-6 – Failure of shop primer before being top coated. The edges of the steel were not stripped to increase primer thickness when the primer was applied. The rust will probably be painted over. Photo by Nick Galizia. 36 • I N T E R FA C E J U LY 2007 be applied directly over an unknown coating without damaging the coating. Will accept most top coats. Back priming: Applying a primer to the back or unexposed side of a substrate. Strip coat: Applying a thin coat to only the inside and outside corners and edges of a substrate prior to coating overall substrate to ensure proper film build. Figures 3-1 through 3-11 show the effects of various coating systems. Typically, a coating system consists of the surface preparation, primer, intermediate coat, and finish coat. Surface preparation is included in the system because it varies with the type of substrate, the type of coating, and ambient and environmental conditions. To keep things simple, the most frequently encountered substrates are listed. These substrates are carbon steel, galvanized steel, wood, concrete block, concrete, brick, coil-coated metal, and aluminum extrusions. The suggested coating systems are for exterior application, are strictly gener- Figure 3-7 – Good contrast of coating systems. The nice-looking finish on the flat roof panels is Kynar®, while the peeling finish on the steel framing is field-applied oil-based paint. Both are approximately the same age. Figure 3-9 – Precast concrete coated with field-applied, acrylic-modified epoxy. Notice that the color is still vibrant after approximately nine years of weathering. Below: Figure 3-8 – Precast concrete painted with an oil-based paint. Delamination due to moisture within the concrete. J U LY 2007 I N T E R FA C E • 3 7 ic, and are not representative of any particular products or manufacturers. The listed coating systems also presume that all proper and recommended surface preparations have been performed prior to application. Coating systems for interior situations are not included because, except for industrial situations, interior coating systems are generally the same for coastal and non-coastal conditions. Of course, all coating systems should be confirmed and verified with the respective coating manufacturer’s product data sheets. Listings are not in any particular order. CONCLUSION Except for the materials used, coating procedures for coastal areas differ little from those for rural and urban areas. Match the coating system with the ambient conditions and select the best coating system the budget can afford. Ensure that proper surface preparation is addressed and that the materials are applied correctly. Many projects are subjected to “value engineering,” and finishes are usually one of the first items to feel the pressure of the budget squeeze. This may be acceptable in some urban and rural areas, but compromising exterior protection in coastal areas should be discouraged. After all, since your project is the best, it deserves the best! REFERENCES AAMA 608.1, American Architectural Metals Association (AAMA). ASTM D4263-83 (199) Standard, American Society for Testing and Materials (ASTM). Charles G. Munger, “Corrosion Prevention by Protective Coatings,” National Association of Corrosion Engineers ( NACE), 1984. Corrosion Basics, An Introduction, National Association of Corrosion Engineers (NACE), 1984. Galvanizing, A Practical Reference For Designers, Galvanizers Association of America. 38 • I N T E R FA C E J U LY 2007 Figure 3-10 – Exterior brick wall painted with alkali-resistant primer and 100 percent, highperformance acrylic. Finish is still sound with little sign of weathering after years. Photo by Nick Galizia. Figure 3-11 – Stamped copper facing that was field painted with an oil-based paint. Paint is faded, curling, and delaminating. Photo by Nick Galizia. International Molybdenum Association Case Studies 05, 06, and 09. Standard AAMA 607.1, AAMA. Technical Notes, Brick Industry Association (BIA), 2000. Volume 1, Good Painting Practice, Steel Structures Painting Council (SSPC). Volume 2, Systems and Specification, SSPC. ACKNOWLEDGEMENTS I extend my sincere gratitude to Charlie Martin, AIA, of McMillan Smith & Partners Architects for creating the graphic sketches; to Angela Napolitano of McMillan Smith & Partners Architects for adding computer graphics; and to my wife, Linda, for editorial review. Their time and contributions to this article are truly appreciated. Joseph “Cris” Crissinger has completed the NACE course of instruction in Protective Coatings and Corrosion Control and is a Construction Materials Specifier with 22 years of experience. As a partner with McMillan Smith and Partners Architects in Spartanburg, Greenville, and Charleston, SC, he evaluates new products and develops all written construction specifications for the firm. His responsibilities also include facility assessment, field investigations, and the coordination of internal training programs. Mr. Crissinger is a Certified Construction Specifier, a Certified Construction Contracts Administrator, and a member of the Construction Specifications Institute, the Building Performance Committee of ASTM, and the Design and Construction Division of the American Society for Quality, and serves in his community on the Construction Board of Appeals for the city of Spartanburg, South Carolina, the board of directors for the Spartanburg Boys’ Home, and the Camp Croft Restoration Advisory Board. Joseph “Cris” Crissinger, CCS, CCCA J U LY 2007 I N T E R FA C E • 3 9 SUBSTRATE PRIMER INTERMEDIATE FINISH Carbon steel 1 coat inorganic, zinc-rich primer 1 coat epoxy polyamide 1 or 2 coats aliphatic polyurethane 1 coat epoxy polyamide primer 1 coat epoxy mastic 1 or 2 coats aliphatic polyurethane 1 coat epoxy polyamide primer 1 coat 100% acrylic high build 1 or 2 coats 100% acrylic high build 1 coat inorganic, zinc-rich primer 1 coat aluminum mastic epoxy 1 or 2 coats aliphatic polyurethane Powder coating Galvanized Steel 1 coat epoxy polyamide primer 1 coat epoxy mastic 1 or 2 coats aliphatic polyurethane 1 coat epoxy polyamide primer 1 coat aluminum mastic epoxy 1 or 2 coats aliphatic polyurethane 1 coat vinyl wash primer 1 coat 100% acrylic high build 1 or 2 coats 100% acrylic high build Powder coating Wood 1 coat alkyd, high-build primer 1 coat 100% acrylic 1 or 2 coats 100% acrylic Concrete Block 1 coat breathable, cementitious, 1 coat breathable, cementitious, Not normally necessary modified epoxy ester modified epoxy ester 1 coat alkali-resistive primer 1 coat heavy-duty, breathable, 1 or 2 coats 100% acrylic high build block filler coating Concrete 1 coat breathable, cementitious, 1 coat breathable, cementitious, Not normally required modified epoxy ester coating modified epoxy ester coating NA 1 coat heavy-duty, breathable, 1 or 2 coats 100% acrylic high build block filler coating Brick 1 coat alkali-resistive primer 1 coat breathable, cementitious, 1 coat breathable, cementitious, modified epoxy ester modified epoxy ester NA 1 coat heavy-duty, breathable 1 or 2 coats 100% acrylic high build block filler Coil-coated metal 2 or 3 coats 70% fluoropolymer NA NA system Aluminum Class I clear or color anodized NA NA Powder coating SUGGESTED COATING SYSTEMS
