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From page 77... ... D-1 Training: Remediation of Soluble Salt Contamination A P P E N D I X D REMEDIATION OF SOLUBLE SALT CONTAMINATION This presentation covers issues related to remediation of soluble salt contamination on steel highway structures. It includes several inter-related sections. Read the entire page →
From page 78... ... D-2 Key Learning Objectives This Training Addresses the Following Questions – When Should Soluble Salts be Remediated on Steel Bridges? – How Effective are Different Methods of Soluble Salt Remediation? Read the entire page →
From page 79... ... D-3 WHEN TO REMEDIATE? Situations calling for Salt Detection and Remediation Good spot to ask people when they have remediated surfaces, for what reasons During Surface Preparation for Coating Before any surface preparation process – Pressure wash salts and other debris prior to mechanical surface preparation – Ensure salt on prepared surface doesn't exceed acceptable levels for coating This may require reworking areas before painting During full coating removal projects – Able to use more effective remediation methods such as: Dry abrasive blasting to an SSPC-SP 10/NACE No 2 condition Wet abrasive blasting SSPC-SP 10 (WAB) Read the entire page →
From page 80... ... D-4 Seasonal Remediation of Salts from Bridge Surfaces Areas subject to winter snow conditions may require seasonal salting for safety – Springtime washing of these salts can prolong steel life – Remediation is typically performed with low pressure water methods May be subject to local environmental restrictions – Visual surface inspections may be appropriate for determining reduction in salt levels Quantitative testing may periodically be used in conjunction with visual inspection to address specific issues In conjunction with washing, areas requiring further remediation and repainting should be identified During Subsequent Coats of Paint Remediate primer and intermediate coats of paint when soluble salt contamination of coating is observed – Pressure wash, low pressure water, or washing with a wet cloth are effective methods Consider soluble salt testing between coats, especially in marine environments, or where primer/intermediate coats are exposed for extended periods of time – Rusted areas may require mechanical preparation Read the entire page →
From page 81... ... D-5 METHODS TO REMEDIATE SOLUBLE SALTS Ways to Efficiently Remove Rust and Salts from Steel Surfaces Mechanical Methods Power Tool Cleaning SSPC-SP 3 SSPC-SP 11 Media Blasting SSPC-SP 10 SSPC-SP 10 (WAB) Read the entire page →
From page 82... ... D-6 Power Tool Cleaning With Rotary Bristle Tool SSPC-SP 11 "Power Tool Cleaning to Bare Metal" Cuts through scale and surface rust Pneumatic tool operated at 90psi spins brush head with needles 3500rpm against surface Difficult to use in tight areas or complex geometries Achieves new surface profile Surface appears visibly cleaned of rust Power Tool Cleaning with Needle Gun SSPC-SP 3 "Power Tool Cleaning" Quickly remediates heavy scaling on surfaces Pneumatic tool operated at 90psi forces metal pins (needles) back and forth against the surface to remove rust and salts – May require additional dust or vacuum shroud Achieves new surface profile Tightly bonded rust and staining remains on the surface after use Not recommended as only step in remedia on of soluble salts due to leaving the surface contaminated Can be useful in ht, complex areas as first step Read the entire page →
From page 83... ... D-7 Power Tool Cleaning Comparison SSPC-SP 3 Needle Gun Remediates well around bolts, crevices, complex and small areas Only remediates loosely adherent rust or chlorides Surface may be visibly dirty after completion SSPC-SP 11 Rotary Bristle Tool Good on flat surfaces but difficult to use around bolts and in tight crevice areas Little to no visible surface rust or chlorides after Both used for spot surface preparation during maintenance and touch up work Media Blast to an SSPC-SP 10/NACE No.2 - Near White Metal Blast Commonly used media used: Aluminum Oxide, Steel Shot, Garnet Abrasive media is propelled against the surface, removing scale and surface rust and re-finishing the surface – Substrate and material used will affect remediation time and final surface profile Final surface shall be 95% free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter. – Surface may contain light shadows in 5% of each 3-inch by 3-inch surface area When viewed without magnification shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter of at least 95% of each unit area. Read the entire page →
From page 84... ... D-8 Water Remediation Methods Four SSPC/NACE standards address water remediations: – SSPC-SP WJ-1/NACE WJ-1 "Waterjet Cleaning of Metals -- Clean to Bare Substrate" – SSPC-SP WJ-2/NACE WJ-2 "Waterjet Cleaning of Metals -- Very Thorough Cleaning" – SSPC-SP WJ-3/NACE WJ-3 "Waterjet Cleaning of Metals -- Thorough Cleaning" – SSPC-SP WJ-4/NACE WJ-4 "Waterjet Cleaning of Metals -- Light Cleaning" Does not produce a new profile, but instead exposes previous abrasive blasted profile on the steel – If pitting has occurred following corrosion of the original substrate, the exposed surface will be pitted All wet methods of bare steel remediation are susceptible to flash rust Specified by visual and non-visual standards of surface cleanliness Visual Near White Metal Blast Cleaned Examples Examples of varying initial surface conditions being remediated to an SP-10 surface, curtesy of SSPC-VIS 1 Dry Abrasive Blast Cleaning Read the entire page →
From page 85... ... D-9 Water Remediation Specifications Descriptions WJ-1 – Surface shall be free of all previously existing visible rust, coatings, mill scale, and foreign matter and have a matte metal finish WJ-2 – 95% of surface shall adhere to WJ 1 – 5% may contain only rust staining, coatings, and foreign matter WJ-3 – 66% of surface shall adhere to WJ 1, with the exception of mill scale – 33% may contain only rust staining, coatings, and foreign matter WJ-4 – Surface shall have all loose rust, loose mill scale, and loose coatings uniformly removed Not to be confused with differences in water pressures Water Pressures used in Remediation LP WC – Low Pressure Water Cleaning – 3,000 to 5,000 psi – Can be used without damaging adherent coating – Recommended for seasonal & partial salt remediation HP WC – High Pressure Water Cleaning – 5,000 to 10,000 psi – Will remove all but tightly adherent rust and coating from the surface UHP WJ – UltraHigh Pressure Water Jetting – >25,000 psi – Highest level of remediation achieved through water methods HP WJ – High Pressure Water Jetting – 10,000 to 25,000 psi – Will remove most coatings, rust, and staining from the surface Not to be confused with WJ-1 through WJ-4 classifications Read the entire page →
From page 86... ... D-10 Non- Visual Specifications of Water Remediated Surfaces SSPC SC-1 – Surface Cleanliness 1 – Surface shall be free of all detectable levels water-soluble chlorides, ironsoluble salts, and sulfates measureable at the field level SSPC SC-2 – Surface Cleanliness 2 – <7 g/cm2 chloride contaminants – <10 g/cm2 soluble ferrous ion salts – < 17 g/cm2 sulfate contaminants SSPC SC-3 – Surface Cleanliness 3 – < 50 g/cm2 chloride or sulfate contaminants SSPC non-visual standards Visual Cleanliness Examples Visual examples of a panel cleaned from WJ-4 through WJ-1 from SSPC-VIS 4 Water Jetting Visual examples of original panel cleaned from WJ-4 through WJ-1 Read the entire page →
From page 87... ... D-11 Solvent Cleaning Methods SSPC-SP 1 Solvent Cleaning – Removal of all oil, grease, soil, drawing and cutting compounds, and other soluble contaminants from the surface – Often termed as a "Solvent Wipe" with acetone or another paint thinner – Solvents remove non-salt contaminants on surfaces as well Addition of Chemicals to low pressure wash water – Acidic and alkaline solutions when added in low concentrations to low pressure wash water can help to dissolve salt ions from the surface Natural Methods Surface salt concentrations can be reduced through natural methods Soluble salt measurements are necessary to determine whether natural methods are reducing salts enough to merit no further remediation Examples include: – Entering into a wet season in certain climates – Spring snow melt Read the entire page →
From page 88... ... D-12 Geometry Effects on Remediation Surface geometry can make it difficult to remediate soluble salts with power tool methods – Corners, crevices, and tight spacing are examples of areas that are difficult to clean with most methods – HEPA vacuum shrouds are often required that limit the ability of tools to clean around obstructions – Crevices may retain water used during remediation with wet methods The location of the contaminated surface may inhibit remediation – Working with power tools may be unsafe – Full containment of the area (e.g., for abrasive blasting) may not be possible – Chemical and/or water run off (e.g., during waterjetting) Read the entire page →
From page 89... ... D-13 Solubility of Salts Some salts are not soluble in water, thus they are more difficult to remediate with wet methods – These salts will not be detected in methods which require the dissolution of salts on the surface being tested – Insoluble salts may or may not affect coating performance If they are visible (e.g., ferric salts) they should be remediated as required to meet the visual requirements of the surface preparation specification Remediation Within Pits or Tight Crevices High levels of pitting will complicate the remediation process Pits tend to trap both corrosion product and salts – Narrower and deeper pits will be more difficult to remediate than wide and shallower pitting – Pitting creates a non-uniform surface which may cause pre-mature coating failure if not remediated Due to this, pits and tight crevices will require extra attention when remediating, similar to the extra attention needed when making salt measurements Read the entire page →
From page 90... ... D-14 Economic Benefits Remediation of Salts Before and during Coating Application – Ensuring a clean and salt free surface will decrease the chance of failures in the coating adhesion, blistering, or through film corrosion in the coating – Increases in the lifetime of the coating and reduces maintenance costs Seasonal Remediation of Salts – Remediation allows visual inspection to parts of the bridge which would otherwise not be available for inspection – Can prolong coating lifetime by reducing salt buildup ECONOMIC BENEFITS OF SOLUBLE SALT REMEDIATION Read the entire page →
From page 91... ... D-15 RECOMMENDED REMEDIATION PRACTICES Full Remediation to Bare Steel 1. Remove corrosion product from heavily corroded areas using mechanical methods such as shipping tools 2. Read the entire page →
From page 92... ... D-16 Remediation Without Coating Removal Low pressure (e.g., 100 psi) wash with water is recommended for salt remediation without coating removal – Pressure washing (e.g., 2000 psi) Read the entire page →
From page 93... ... Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing America's Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) Read the entire page →
From page 94... ... TRA N SPO RTATIO N RESEA RCH BO A RD 500 Fifth Street, N W W ashington, D C 20001 A D D RESS SERV ICE REQ U ESTED 4804377803099 ISBN 978-0-309-48043-7 90000 N O N -PR O FIT O R G . Read the entire page →

From page 77...

... D-1 Training: Remediation of Soluble Salt Contamination A P P E N D I X D REMEDIATION OF SOLUBLE SALT CONTAMINATION This presentation covers issues related to remediation of soluble salt contamination on steel highway structures. It includes several inter-related sections.