Spot Painting to Extend Highway Bridge Coating Life: Volume 2: Research Overview (2018)

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NCHRP Project 14-30 B-1 APPENDIX B Laboratory Test Protocol for Repair Test Coatings

NCHRP Project 14-30 B-2 Recommended Practice for Testing and Evaluating Spot Coatings over Substrates with both Previously Corroded Steel Prepared by SSPC-SP 3 Power Tool Cleaning and Existing Coatings Using Flat Panel Specimens 1.0 Scope 1.1 This practice covers specific procedures for using cyclic salt fog/UV exposure and salt fog testing to evaluate coatings applied on power tool cleaned corroded steel and existing coatings. The former test method is intended to determine the suitability of coatings for repair service in spot painting operations involving conditions of bold exposure (direct UV exposure and condensation/evaporation). The latter test method is intended to determine the suitability of coatings for repair service in spot painting operations involving conditions high exposure to chlorides, extended time of wetness and inconsequential UV exposure. This test procedure is intended to identify suitably performing coatings/systems for use in spot repairs of existing coatings on bridges. The two test methods, when performed together will provide a good indication of the ability of coatings/systems to perform over specific coating types on corroded, salt-contaminated steel given minimal surface preparation. The testing is intended for spot repair coatings applied to bridges for atmospheric exposure in mild or moderate environments. Existing coatings on bridges may have compatibility issues with test coatings not revealed in these tests even if the “existing” coating used in laboratory is of the same generic type and performed satisfactorily with the test “repair” coatings. The use of field test patches per ASTM D5064, “Standard Practice for Conducting a Patch Test to Assess Coating Compatibility” is recommended to address that possibility. 1.2 This practice addresses the methods of obtaining, measuring, and controlling exposure conditions as well as specimen preparation and evaluation of results. It does not address qualification of coatings based upon test results. 1.3 The values in this document include both English and SI units based upon their conventional use. 1.4 This method does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2.0 Referenced Documents 2.1 ASTM Standards ASTM A572 Specification for High Strength Low-Alloy Columbium-Vanadium Steel B117 Standard Practice of Operating Salt Spray (Fog) Apparatus D610 Standard Practice for Evaluating Degree of Rusting on Painted Steel Surfaces D714 Standard Test Method for Evaluating Degree of Blistering of Paints D4587 Standard Practice for Fluorescent UV-Condensation Exposures of Paint and Related Coatings D5064 Standard Practice for Conducting a Patch Test to Assess Coating Compatibility D7091 Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals G85 Standard Practice for Modified Salt Spray (Fog) Testing

NCHRP Project 14-30 B-3 G154 Standard Practice for Operating Fluorescent Light Apparatus for UV Exposure of Nonmetallic Materials 2.2 SSPC Standards SSPC PA-15 Material and Preparation Requirements for Steel Test Panels Used to Evaluate the Performance of Industrial Coatings SSPC-SP 3 Power Tool Cleaning SSPC-SP 5 White Metal Blast Cleaning SSPC Technology Guide 15 Field Methods for Retrieval and Analysis of Soluble Salts on Steel and Other Nonporous Substrates SSPC-VIS 3 Guide and Reference Photographs for Steel Surfaces Prepared by Power and Hand Tool Cleaning 2.3 Other Documents Coating manufacturer product and safety data sheets 3.0 Summary of Practice 3.1 Cyclic corrosion/UV exposure shall be performed per ASTM D5894. The test specimens are exposed to alternating periods of one week in a fluorescent UV/condensation chamber and one week in a cyclic salt fog/dry chamber. The fluorescent UV/ condensation cycle is 4-hr UV at 0.89 W/(m2· nm) at 340 nm at 60°C and 4-hr condensation at 122o F (50° C), using UVA-340 lamps. The fog/dry chamber runs a cycle of 1-hr fog at ambient temperature and 1-hr dry-off at 95o F (35° C). The fog electrolyte is a relatively dilute solution, with 0.05 % sodium chloride and 0.35 % ammonium sulfate. 3.2 Salt fog shall be performed per ASTM B117. The test specimens are continuously exposed to a spray of fog electrolyte with 5.0% chloride. The temperature in the test chamber will be maintained at 95 + 3o F (35 + 1.67° C). 4.0 Significance and Use 4.1 Typical bridge spot painting requires the application of repair coatings on surfaces with failed areas consisting of rusted steel, existing coatings and failure boundaries. Prior to applying repair coatings, the repair area receives cleaning treatments including mechanical surface preparation performed on the rusted area with some overlap past the failure boundary into the existing coating. The transition area is typically feathered to facilitate proper application of the repair coatings. The repair coatings are applied over the prepared substrate. SSPC-SP 3 is a common method for surface preparation prior to application of repair coatings used for atmospheric exposure. The exposure conditions for spot painting bridges vary between direct UV exposures with condensation/ evaporation cycles to sheltered locations with inconsequential UV exposure and high time of wetness. This practice is intended to provide realistic simulations of the interaction of those factors including the presence of moderate soluble salt contamination (after surface preparation). 4.2 Results obtained from this practice can be used to compare the relative durability of coating materials in typical bridge environments. They can also be used to establish thresholds for

NCHRP Project 14-30 B-4 acceptable coating performance. 4.3 The practice includes the use of selected coating systems to replicate existing coating systems on bridges. The selection of those coating systems is left to the user. It should be noted that spot coating repairs are typically applied to coatings that have been in service for extended periods. Even if identical samples of existing coatings would be available for use in this practice, service-related deterioration and other factors may interact to provide different results in the field from those obtained in the laboratory. This practice is not intended to provide final proof of compatibility between the candidate repair coatings and existing coatings on bridges. That issue should be addressed by the use of test patches as noted in Section 1.1. 4.4 Coatings passing this test protocol are anticipated to exhibit good durability as spot repair coatings compared to those which fail to exhibit comparative durability during testing. It should be noted that field applications involve complex interactions and laboratory results may not be reflected in field performance. 4.5 Comparisons in performance of coatings between test runs can be difficult. In those instances, it is desirable to use a control repair coating system (and existing coating system) to ensure a relative comparison in coating performance between the test runs. 5.0 Apparatus 5.1 Fluorescent UV-Condensation Exposure Chamber, complying with Practice G154 with modified mounting brackets (with the exposure windows removed) 5.2 UVA-340 Fluorescent Lamps 5.3 Salt Fog/Dry Cabinet complying with Practice G85 6.0 Test Specimens 6.1 The testing should use hot-rolled steel panels made from ASTM A572 high-strength low alloy columbium-vanadium steel (50 grade). A minimum of six panels will be required for the testing with a sufficient number of additional panels used for salt contamination testing during test panel conditioning. The steel panels should measure - 6 in. (15.24 cm) x 4 in. (10.16 cm) x 1/4 in. (0.64 cm). 6.2 Workers performing surface preparation and coating application work should be equipped with the proper personal protection equipment. 6.3 Test panels, including those used for salt contamination testing, shall have the mill-scale removed from the test face by blast cleaning to an SSPC –SP 5 condition. The back faces and edges of the panels should receive a protective coating to prevent rust staining during the panel conditioning and testing. Coatings replicating existing coatings on bridges should be applied to half of the test surface of each panel (per manufacturer instructions) with the remainder of the surface consisting of blast-cleaned steel uncoated as shown in Figure 1. The panels used for salt contamination testing should not have their test faces coated. Those coatings should be cured in ambient conditions for 28 days at ambient/room temperature conditions 72 + 2° F (22.2 + 1° C).

NCHRP Project 14-30 B-5 The panels should be conditioned per ASTM G85 Annex 5 for 250 hours of exposure in accordance with ASTM D5894. The fog/dry chamber runs at a 1-hour cycle of fog spray at ambient temperature ~ 72o F (22.2o C ) and 1-hour dry off at 95o F (35° C). The fog electrolyte was an aqueous solution of 0.05 % sodium chloride and 0.35 % ammonium sulfate. Deionized water should be used for panel conditioning and the entire test program (0-5 µS/cm conductivity). During conditioning, the exposed steel portion of the test panels should be positioned above the painted portion which should be affixed to the mounting brackets. The painted portion of the test panels should be masked during the condition process to prevent staining from rust bleeding. Care should be taken to prevent rust bleeding from damaging components in the dry/fog chamber. After 100 hours in the test chamber, the salt contaminated panels should be inspected. If the panels do not have a continuous rust film, condition them for an additional 50 hours. If they have a continuous rust film, the panels should be inspected for initial condition per SSPC-VIS 3 (Conditions C or D). The condition should be noted and three salt-contamination panels extracted for evaluation. Then, the rusted surfaces should be prepared to SSPC-SP 3 surface preparation by power wire brush cleaning to SSPC VIS 3 end condition SP 3/PWB. The surfaces of the three panels should be tested for soluble salt contamination pursuant to SSPC: TECHNOLOGY GUIDE 15 using either sleeve methods 5.2.5.1, 5.2.5.3 and 5.2.5.4 for chlorides, nitrates and sulfates respectively or the patch method 4.2.2. The results can be reported in µg/cm2 or µS/cm depending on the testing method used. If the chloride contamination is less than 20-30 µg/cm2 (~166 to 250 µS/cm), the conditioning should be continued and testing of additional test panels repeated every additional 50 hours until the specified chloride Exposed Test Surface of Existing Coating 3 in. Weathered Existing Coating 3 in. Rusted Steel/ Mill Scale Cleaned Per SSPC SP 3 1 in. SSPC SP 3 Cleaning Overlap/Feathering over Existing Coating (max.) 5 in. Spot Coating 6 in. REF. 4 in. REF. Spot Coating over Existing Coating Spot Coating over Rusted Steel/Mill Scale Cleaned Per SSPC SP 3 Figure 1. Test Panel Layout (0.25 in.-Thick Steel)

NCHRP Project 14-30 B-6 contamination range is achieved. If the chloride contamination is in the range of 20-30 µg/cm2 (~166 to 250 µS/cm), the conditioning process should be stopped and the masking tape removed from the boundaries and existing coating. SSPC-SP 3 surface preparation should be applied to the rusted portion of the panels slightly overlapping the existing coating. The prepared surface should be visually inspected per SSPC-VIS 3. The boundary between the existing coating and prepared surface should be feathered by hand abrading using 100 grit sand paper. The combination of power tool- cleaning and feathering should extend over approximately 1-inch of the existing coating as shown in Figure 1. Store the cleaned panels in a dry environment prior to applying the test coatings. If the user intends to perform salt remediation treatments on the rusted surfaces in the field prior to or after SSPC-SP 3 surface preparation, additional salt contamination test panels can be added to the conditioning process. The rusted surfaces can be treated either prior to, or after SSPC-SP 3 surface preparation. If this step is added, all the test panels should be treated in a similar manner prior to application of the test repair coatings including initial salt contamination testing to ensure the appropriate level has been achieved. After treatment, the salt levels should be tested on the treated contamination test panels and recorded as noted previously. This is an optional step for the user. Application of the test repair coatings can be performed on the test panels in either the horizontal or vertical position at the option of the user. Prior to painting, the prepared surface should be inspected to ensure that it has not rusted back. The test face should be wiped with a solvent (lacquer thinner) to serve as a final cleaning step and remove any oils from handling. Measurements should be taken of ambient temperature, relative humidity, coating temperature and surface temperature of the test panels. Application conditions should be per the coating manufacturer’s product data sheets. At a minimum, the surface temperature of the test panels should be 5o F (2.8o C) above the dew point for painting to commence. Painting conditions should be monitored and recorded at the beginning and throughout the painting process at 2-hour intervals. The coatings should be mixed or agitated per the manufacturer’s instructions. Application of the test repair coatings can be performed by brushing, rolling or airless spraying. If spraying is used a 1-in. (2.54 cm) strip of the existing coating should be masked to prevent it from being painted. During application of each coat of the repair coating (if multiple coats are applied), the coating thickness should be measured using a wet film thickness gage to verify the application is within the manufacturer’s guidelines. Any surface coating imperfections can be repaired by brushing. After the liquid-applied coatings cure to the dry-to-handle condition, dry film thicknesses should be measured on each panel per ASTM D7091. For each panel, five readings should be taken over the SSPC-SP 3 cleaned portion — one near each corner of the repair test coating and one in the center. For coatings that do not hardened sufficiently to permit testing, the user can rely on wet film thickness readings taken with the tooth gages during painting to ensure that coating was properly applied. After the panels are approved for testing, they should be cured under ambient/room temperature conditions 72 + 2o F (22.2 + 1o C) for 28 days. The edges of the panels should be covered with electrical tape or dipped in epoxy and the panels photo- documented for condition tracking. Application of non-traditional coatings (greases or tapes) can be occur shortly before the onset of the performance testing as they do not require cure times. Prior to their application, the test panels should be wiped with lacquer thinner. Electrician’s tape should be placed around the edges of the test panels prior to the grease application to prevent rusting and rust bleed onto the specimen

NCHRP Project 14-30 B-7 test surfaces. Application conditions should be monitored — as with liquid-applied coatings — with applications being performed when the surface temperature of the specimens is 5o F above the dew point to ensure that these coatings are not applied over moist substrates. Greases can be applied using a spatula and the thickness measured with a tooth gage. If no guidance exists for application thicknesses, greases should be applied at thicknesses between 20-40 mils (500-1,000 microns) as measured by wet film thickness gages. Tapes need to be cut to size from parent rolls or sheets. They should be applied according to manufacturer instructions. A small wallpaper roller can be run over the applied tape to ensure firm adherence, and that no air pockets are present at the tape/substrate interface. If spray-on adhesives are used, some curing time may be necessary for the adhesive to set. Prior to testing, the panels with these coatings should be photo-documented for condition tracking. 7.0 Procedure 7.1 For accelerated performance testing using cyclic salt fog/UV exposure, three panels of existing coatings/repair test coatings should be tested for 15 two-week-long cycles (5,040 total hours) using ASTM D5894. The panels should be initially placed in fluorescent UV-condensation exposure chambers and subject to one-week (168 hours) of exposure in accordance with ASTM D4587. The chambers are to be equipped with UVA 340 bulbs and calibrated to operate at a normal irradiance (0.89 µm). Standard test panel mounting brackets should to be modified with the exposure windows removed. The panels should be placed with the repair test coatings closest to the bulbs for maximum UV exposure. The test chambers should be set to operate on a repetitive cycle of UV exposure at 140° F (60° C) for four hours alternated with a four-hour condensation cycle at 122° F (50° C) using potable water. Thereafter, the test panels should be rotated to fog/dry chambers for a week-long exposure per ASTM G85. The panels should be mounted with the existing coatings end of the panels inserted in the chamber mounting brackets allowing the repair test coatings to receive the greatest exposure to the cyclic salt fog during the condensation cycle. The cyclic exposure consists of one-hour of condensation of fog sprayed from a single nozzle located in the center of the chamber. This is followed by one hour of evaporation (drying) at 95° F (35° C)with moisture being exhausted from the chamber. Once the cyclic salt fog testing is completed, the panels should be returned to the fluorescent UV- condensation exposure chambers for further testing or temporarily removed for panel evaluation prior to continued testing. Each two-weeks of fluorescent UV-condensation exposure chambers-fog/dry exposures constitute one cycle of testing. 7.2 For accelerated performance testing using salt fog exposure, three panels of existing coatings/repair test coatings should be tested continuously for 5,040 hours (except for periodic evaluations) using ASTM B117. A 5% aqueous salt solution is to be continually fogged in appropriately equipped fog chambers. The testing should be performed at ambient temperature measured at 92°- 98°F (33.3°-36.7° C) during the test program by data loggers placed in the test chambers. The salt solution should be replenished in the test chamber spray tanks in a timely manner and periodic checks need to be made for solution pH and spray volume. 8.0 Duration of Exposure/Evaluations 8.1 At 1,008-hour (6-week) intervals, the panels should be temporarily removed from the test chambers for nondestructive evaluation of repair test coating performance and photo documentation. Coating performance should be evaluated for rust according to ASTM D610 and for blistering according to ASTM D714. Failure is to be set at a rust grade of 5 or less (1- 3% without classifying type) and blistering at a “dense” rating. A repair test coating that fails by either of those methods/criteria is considered to have failed and the duration of the repair testing

NCHRP Project 14-30 B-8 coating in 1,008-hr intervals will be reported along with performance of the set of test panels up to failure. A repair test coating that is found to fail in the 3,024-hour evaluation is deemed to have performed for 2,016 hours without failure. After 5,040 hours of total exposure, the testing is complete and the final evaluations are performed. Repair test coatings that pass the final evaluation with no failures are deemed to have passed the test protocol. Any test panel failures/mechanisms should be noted for reporting/evaluation purposes. The user can elect to apply different failure criteria. 9.0 Reporting 9.1 Reporting of repair coating test performance should address the following: 1. The conditioning of the test panels prior to coating application a. The dates of the work (beginning-ending) b. The existing coatings applied (manufacturer and product/safety data sheets) c. The steel used (type, panel dimensions and mill certification) d. Conditioning hours prior to achieving the target chloride surface contamination e. The surface preparation used (SSPC type and power tool(s) used) f. The soluble salt surface contamination (concentrations/types) g. The use of a salt remediation treatment (when used/method/resulting soluble salt concentrations) 2. The coating application and condition of the applied repair test coatings a. The date(s) of the work (beginning-ending) b. Types of repair test coatings used with specific existing coatings (manufacturer & product/ safety data sheets) c. Application environmental conditions d. Method of application e. Thicknesses of each applied coat of the repair coating system f. Curing time and conditions g. Pictures of the prepared panels prior to testing 3. The coating test program and periodic evaluations of the repair test coatings a. The dates of the initiation and conclusion of the test procedure b. Information about the test chambers used and last calibration dates c. Descriptions of consumable materials including salts and water d. Descriptions of any equipment stoppages or other interruptions occurring during the test program e. Descriptions of any problems/unusual observations encountered during testing (Note that failure of an exposed existing coating does not reflect on the performance of the repair test coating) f. Results of test periodic test evaluations and pictures of test panels at each evaluation 4. A summary of the final test results a. Identification of the existing/repair test coatings evaluated b. Tabularized summaries of those systems noting the test method used, the number of test cycles passed, and the number and types of repair coating failures within each 1,008-hr test cycle c. Comparative ranking of repair test coatings (if performed) and listing of any of those coatings that passed the 5,040-hr test program (including the types of any failures that were encountered)