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From page 10... ... NCHRP Project 14-30 10 3.0 COATINGS FOR SPOT PAINTING Coating selection is vital for successful bridge spot painting. Coatings have a wide range of properties that affect not only performance after they are cured, but also application constraints the agencies must deal with. Read the entire page →
From page 11... ... NCHRP Project 14-30 11 • Surface preparation • Soluble salt contamination • Work environments/conditions • Surface tolerance • Application requirements • Painter skill/coating friendliness • Project costs. Read the entire page →
From page 12... ... NCHRP Project 14-30 12 Coating Type Uses Advantages Limitations Comments Acrylics Primer, Intermediate Coat, Finish Coat • one-component coatings • low VOCs • user friendly • durable topcoats • excellent UV resistance • can be used as a topcoat over other coating types • low temperature/humidity restrictions for application • not suited over salt contaminated steel • not recommended for immersion or severe industrial atmospheres or over old paints where good wetting is needed Acrylic systems can be used in regions with restrictive VOC regulations. Top coats are commonly used with other coating types. Read the entire page →
From page 13... ... NCHRP Project 14-30 13 Coating Type Uses Advantages Limitations Comments Epoxy Mastics Primer, Intermediate Coat, Finish Coat* • Surface tolerant • Good wetting properties • Can be applied to high builds in several coats • Low VOC formulations available • Excellent chemical resistance • Excellent moisture resistance • Slower drying than regular epoxies • Longer recoat times than regular epoxies • High builds over aged alkyds can result in disbonding. Read the entire page →
From page 14... ... NCHRP Project 14-30 14 Coating Type Uses Advantages Limitations Comments Zinc-rich Coating (Epoxies) Primer • excellent corrosion resistance • excellent for corrosive environments • self-healing/galvanic protection • two- or three-component coatings • limited pot lives • should be applied over profiled steel • not recommended for immersion service Zinc-rich epoxy primers are typically applied by airless spraying. Read the entire page →
From page 15... ... NCHRP Project 14-30 15 3.1.1 Penetrating Sealers Epoxies, moisture-cure polyurethanes and calcium sulfonates are available as penetrating sealers usually containing no or little pigmentation allowing them to readily penetrate into rust and crevices and seal those surfaces. As they are readily applied at minimal coat thicknesses, typically 1-3 mils (25-75 microns) Read the entire page →
From page 16... ... NCHRP Project 14-30 16 the steel. This requires either abrasive blasting (typically SSPC-SP 6, "Commercial Blast Cleaning," SSPC-SP 10, "Near-White Blast Cleaning," or SSPC-SP 14, "Industrial Blast Cleaning") Read the entire page →
From page 17... ... NCHRP Project 14-30 17 contamination. Low-level surface preparation may not adequately prepare the surface or reduce the level of soluble salt contamination. Read the entire page →
From page 18... ... NCHRP Project 14-30 18 Coating System Coating Materials Comments 1 coat • Epoxy mastic • excellent corrosion protection (barrier) • good resistance to soluble salt contamination • not durable for direct UV exposure • commonly pigmented with aluminum or MIO 2 coat • epoxy primer • two-component polyurethane or acrylic finish coat • excellent corrosion protection • good resistance to soluble salt contamination • excellent UV resistance • moisture-cure polyurethane primer • moisture-cure polyurethane or, two-component polyurethane or acrylic finish coat • good corrosion protection • good resistance to soluble salt contamination • excellent wetting properties for application (aluminum pigmented primer) Read the entire page →
From page 19... ... NCHRP Project 14-30 19 • Surface conditions acceptable for coating (e.g., tolerance of limited salt contamination) • Compatibility with existing coatings • Atmospheric conditions that permit painting • Application by brush, roll, or spray • Environmental friendliness • Number and severity of worker safety issues • Ease of coating preparation for painting (e.g. Read the entire page →
From page 20... ... NCHRP Project 14-30 20 Coating Type surface cleanliness acceptable for coating compatibility with existing coatings atmospheric conditions that permit painting application by brush, roll or spray environmentally friendliness number and severity of worker safety issues ease of coating preparation for painting minimal overspray problems ability to coat complex substrates and crevices application tolerance speed of curing ease of coating repair ease of cleanup Acrylic primers F G G E E E E E F G F G E Acrylic finish coats G G G E E E E E N/A G F G E Alkyd primers G G G G G G E G E G F G G Alkyd topcoats G G G G G G E G N/A F F G G Calcium sulfonate alkyds F G G F G G E G E E P G G Epoxy primers/intermediate coats G F G G G F F P G G G F F Two-component polyurethane primers G F E G F F F P G F E F F Two-component polyurethane finish coats G N/A E G F F F P N/A F E F F Moisture-cure polyurethane primers/intermediate coats G F E G F F E P E F E F F Moisture-cure polyurethane finish coats G N/A E G F F E P N/A F E F F Zinc-rich epoxy primers F N/A G F F F F P N/A G G F F Zinc-rich moisture-cure polyurethane primers F N/A E F F F F P N/A G E F F Note: E=Excellent, G=Good, F=Fair, P=Poor, N/A= Not Applicable Table 4. User Friendliness of various generic coatings. Read the entire page →
From page 21... ... NCHRP Project 14-30 21 3.5 Service Life Expectations of Spot Coating Systems Spot painting repairs using 1- and 2-coat systems over marginally prepared substrates are expected to last approximately 5 to 7 years based upon the quality of the repair and the severity of the micro- and macro-environments. Use of 3-coat systems using zinc primers and profiled steel substrates may extend the expected service life up to about 15 years. Read the entire page →
From page 22... ... NCHRP Project 14-30 22 Soluble salt contamination levels are typically stated in units of micrograms per square centimeter (µg/cm2) and are often ion specific (chloride, sulfate, nitrate, etc.) Read the entire page →
From page 23... ... NCHRP Project 14-30 23 corrosion may also be present at locations having coating failures. Under those circumstances marginal surface preparation and use of coating systems in Table 3 are recommended. Read the entire page →
From page 24... ... NCHRP Project 14-30 24 - Full coating failures should receive marginal substrate repairs feathering the intact existing coating followed by repair using a coating/system provided in Table 3. See Factor 2. Read the entire page →
From page 25... ... NCHRP Project 14-30 25 3.8 Climate Restrictions for Spot Coatings Climatic conditions play a significant role in the selection of coatings. They affect: • Conditions under which a coating can be applied -- Coatings should not be applied in rain, wind, snow, fog, or mist, or when the substrate temperature is less than 5o F above the dew point. Read the entire page →
From page 26... ... NCHRP Project 14-30 26 3.9.1 Tapes Tapes are typically thick (up to several hundred mils) Read the entire page →
From page 27... ... NCHRP Project 14-30 27 3.9.3 Conversion Coatings Conversion coatings used in highway applications are typically rust convertors containing tannic acid combined with an acid-tolerant binder, such as a vinyl emulsion. The tannic acid converts the rust to iron tannate, a stable blackish corrosion product. Read the entire page →
From page 28... ... NCHRP Project 14-30 28 • Product Description -- This describes the type of coating (e.g., primer, intermediate, and finish coat) , its binder/resin, and any further definitions that would assist the user in determining its function (e.g. Read the entire page →
From page 29... ... NCHRP Project 14-30 29 Section 2 -- Hazard(s) identification includes all hazards relevant to the chemical; required label elements. Read the entire page →
From page 30... ... NCHRP Project 14-30 30 Section 15 -- Regulatory information. Read the entire page →

From page 10...

... NCHRP Project 14-30 10 3.0 COATINGS FOR SPOT PAINTING Coating selection is vital for successful bridge spot painting. Coatings have a wide range of properties that affect not only performance after they are cured, but also application constraints the agencies must deal with.