Priming and Painting Slip Critical Steel Connections 10 May 2012 Troy Fraebel Corrosion Specification Specialist 25 years in industrial coatings SSPC Protective Coatings Specialist SSPC C-1 and C-2 Instructor NACE Certified Coatings Inspector Former AWWA D-102 Voting Member 13 Years with KTA-Tator, Inc. 3.5 Years with Caldwell Tanks Incorporated in 1866 Henry Sherwin Edward Williams 1
Over 3,325 Service Centers With Dedicated Protective & Marine Representatives The Protective & Marine Group is Dedicated to Providing Coatings for the Prevention of Corrosion, which Results in the Loss of $300+ Billion Annually Research & Development John Breen Tech Center, Cleveland AW Steudel IM Lab, Chicago Warrensville Lab, Cleveland 2
Agenda Structural Joints Using High Strength Bolts and Coatings Qualified for Class A or Class B Slip Surface Preparation of Steel (SSPC-SP 1 to SP 15) Steel Primers Zinc-rich Epoxy MCU Alkyd Acrylic High Performance Steel Topcoats Fluoropolymers Polysiloxanes Polyurethanes Acrylic Slip-Critical Joint A joint that transmits shear loads or shear loads in combination with tensile loads in which the bolts have been installed... to provide a pretension in the installed bolt (clamping force on the faying surfaces), and with faying surfaces that have been prepared to provide a calculable resistance against slip. 3
Standards Organizations Involved Familiarity with the referenced AISC, ASCE, ASME, ASTM and SSPC specification requirements is necessary for the proper application of this Specification. From the Glossary Faying Surface. The plane of contact between two plies of a joint. Coated Faying Surface. A faying surface that has been primed, primed and painted or protected against corrosion, except by hot-dip galvanizing. i Mean Slip Coefficient. μ, the ratio of the frictional shear load at the faying surface to the total normal force when slip occurs. 3.2.2. Slip-Critical Joints The faying surfaces of slip-critical joints as defined in Section 4.3, including those of filler plates and finger shims, shall meet the following requirements:...... (b) Coated Faying Surfaces: Coated faying surfaces shall first be blast cleaned and subsequently coated with a coating that is qualified in accordance with the requirements in Appendix A as a Class A or Class B coating as defined in Section 5.4. 4
Why Blast Clean? Clean and Profile Paints Adhere to the Surface by Mechanical and / or Chemical Bond Whatever interferes with mechanical or chemical bond will, in turn, interfere with adhesion. SSPC-SP 1 SSPC-SP 2 SSPC-SP 3 SSPC-SP 5 / NACE 1 SSPC-SP 6 / NACE 3 SSPC-SP 7 / NACE 4 SSPC-SP 8 SSPC-SP 10 / NACE 2 SSPC-SP 11 SSPC-SP 12 / NACE 5 SSPC-SP 14 / NACE 8 SSPC-SP 15 SSPC-SP 16 Standards Solvent Cleaning Hand Tool Cleaning Power Tool Cleaning White Metal Blast Cleaning Commercial Blast Cleaning Brush-Off Blast Cleaning Pickling Near-White Blast Cleaning Power Tool Cleaning to Bare Metal Surface Preparation and Cleaning of Steel and other Hard Materials by High and Ultra High Water Jetting Industrial Blast Cleaning Commercial Power Tool Cleaning Brush-Off Blast Cleaning of Coated and Uncoated Galvanized Steel, Stainless Steels, and Non-Ferrous Metals SSPC-SP1 Solvent Cleaning Solvent Cleaning is a method for removing all visible oil, grease, soil, drawing and cutting compounds, and other soluble contaminants from steel surfaces. It is the first step by definition in every preparation method! 5
SSPC-SP2 Hand Tool Cleaning Hand Tool Cleaning removes all loose mill scale, loose rust, loose paint, and other loose detrimental foreign matter. It is not intended that adherent mill scale, rust, and paint be removed by this process. Mill scale, rust, and paint are considered adherent if they cannot be removed by lifting with a dull putty knife. SSPC-SP3 Power Tool Cleaning Power Tool Cleaning removes all loose mill scale, loose rust, loose paint, and other loose detrimental foreign matter. It is not intended that adherent mill scale, rust, and paint be removed by this process. Mill scale, rust, and paint are considered adherent if they cannot be removed by lifting with a dull putty knife. SSPC-SP 7 / NACE 4 Brush-Off Blast Cleaning has the same definition. Appropriate for LARGE areas. The entire surface shall be subjected to the abrasive blast.... When a coating is specified, the surface shall be roughened to a degree suitable for the specified coating system. SSPC-SP6 Commercial Blast A Commercial Blast cleaned surface, 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, except for staining as noted below random staining shall be limited to no more than 33% of each unit area of surface (9 in 2 ), and may consist of light shadows, slight streaks, or minor discolorations caused by stains of rust, stains of mill scale, or stains of previously applied coatings 6
SSPC-SP10 Near-White Blast A Near-White Blast cleaned surface, 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, except for staining as noted below random staining shall be limited to no more than 5% of each unit area of surface (9 in 2 ), and may consist of light shadows, slight streaks, or minor discolorations caused by stains of rust, stains of mill scale, or stains of previously applied coatings SSPC-SP5 White Metal Blast A White Metal Blast cleaned surface, 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. AASHTO R31 for Evaluation of Protective Coating Systems for Structural Steel requires abrasive blast cleaning to achieve a White Metal Blast using 100% S280 steel shot to produce a 2 3.5 mil surface profile for the slip coefficient test. Steel shot was selected to produce a peened surface texture (lower peak density) to create a worst case scenario. Centrifugal Blast Cleaning Shops will often combine steel shot and grit for blasting. The shot impacts the mill scale while the grit imparts profile. 7
Centrifugal Blast Cleaning Savings of time, labor, energy, and abrasive Superior, more uniform cleaning Reduces blast waste by recycling abrasive Protects of the environment Active/Anodic Magnesium Zinc Aluminum Cadmium Tin Lead Steel Iron Copper 410 Passive 304 Passive Silver Graphite Gold Platinum Passive/Cathodic Mill Scale SSPC-VIS 1 8
The plies of slipcritical joints with coated faying surfaces shall not be assembled before the coating has cured for the minimum time that was used in the qualifying tests. AASHTO R31 specification requires curing at 25 +/ 2 C and 65 +/ 5% relative humidity. 1985 Publication now modified and APPENDIX A of Specification for Structural Joints Using High-Strength Bolts Appendix A Purpose and Scope The purpose of this testing procedure is to determine the mean slip coefficient of a coating for use in the design of slipcritical joints. Adherence to this testing method provides that the creep deformation of the coating due to both the clamping force of the bolt and the service-load joint shear are such that the coating will provide satisfactory performance under sustained loading. 9
Definition of Essential Variables The time interval between application of the coating and the time of testing The coating thickness... per SSPC PA2.. is 2 mils less than the average thickness The specimens are to be coated to an average thickness that is 2 mils greater than the maximum thickness to be used in the structure on both of the plate surfaces(the faying and outer surfaces) Coating Composition and Method of Manufacture Testing Configurations Contact Surface of Bolted Parts Class A- Slip Coefficient not less than 0.33 0.30 per AISC Clean Mill Scale and Blast Cleaned Surfaces with a Class A Coatings Class B- Slip Coefficient not less than 0.50 Blast Cleaned Surfaces and Blast Cleaned Surfaces with Class B Coating Class C-Slip Coefficient not less than 0.35 Hot Dipped Galvanized Steel and roughened surfaces 10
NO Masking Reduced Cost How Coatings Protect Surfaces Barrier Inhibitive Sacrificial Corrosion Prevention Stop the deterioration of a substrate. Corrosion is a natural process that displays the tendency of materials to give up energy and return to its natural state. 11
Barrier Most coatings serve as a protective barrier by isolating the metal from the environment. Film reinforcement further slows this action down. This can also be true when protecting concrete, wood or other substrates. Inhibitive Some pigments used in manufacturing primers control corrosion by forming inhibitive compounds. These compounds are slightly soluble in water, and upon contact with water vapor, passivate the substrate. Rust inhibitive primers should never be specified or recommended for use in immersion service. Sacrificial When a zinc coating is applied to steel, the zinc, being more active than the steel, sacrifices itself to protect the steel from corrosion. This is based on the galvanic series. Active/Anodic Magnesium Zinc Aluminum Cadmium Tin Lead Steel Iron Copper 410 Passive 304 Passive Silver Graphite Gold Platinum Passive/Cathodic 12
Class B Primers Two or three-component, solvent-based, inorganic, ethyl silicate, zinc-rich coating Two or three-component, water-based, inorganic, zinc silicate coating Two or three-component catalyzed polyamide epoxy, organic zinc-rich coating Three-component water based organic amine adduct zinc-rich coating Moisture-cured urethane (MCU) zinc primer Non-zinc Epoxy Primer Zinc-Rich Primers Contain High Percentage of Zinc Dust in the Dried Film So That There Is Direct Contact Between Zinc Particles and Steel (SSPC Guide 12.00 Guide to Zinc-Rich Coating Systems: Organic zinc-rich primers must contain 77% zinc and inorganic zinc-rich primers must contain 74% zinc in the dried film) Sacrificial / Galvanic Protection (like galvanizing) Corrosion Protection Prevention of Undercutting How Zinc-Rich Primers Cure IOZ = Solvent Evaporation / Moisture Curing or CO 2 OZ = Solvent Evaporation / Chemical Reaction (Epoxy) Solvent Evaporation / Moisture Curing (MCU) 13
Corrosion Rate of Zinc vs. ph osion Rate Relative Corr 60 50 40 30 20 10 0 0 2 4 6 8 10 12 14 16 ph IOZ Zinc Rich Primers Better Surface Preparation Required (Requires Angular Surface Profile) Requires Special Application and Mixing Equipment Recommended ph Range of 5.0-9.0 (untopcoated) Prone to Mud Cracking at high DFT Shop Application Performance Similar to Galvanizing Heat Resistance to 750 F Low Temperature Application Fabrication Shop Paint Booth Application of Zinc Rich Primer 14
Organic Zinc Rich Tolerates Less Stringent Surface Preparation Used to Touch-up Inorganic Zinc (IOZ) Moisture Cured Polyurethanes Can be applied during high humidity Ease of Application Fast Recoat / Fast Cure Times Low Temperature Application 20 F. Single Package Zinc-Rich Available Special Reducers Required Unused Portion Has Limited Shelf Life Needs Relative Humidity to Cure Class A Primers Standard two-component fast cure epoxy 15
Epoxy Primers Epoxy Resins or Emulsions of Epoxy Resins Which Cross-Link with Polyamides, Amines, or Other Hardeners. They Cure by Polymerization - The chemical joining of polymer chains Catalyzed Epoxies Epoxy Resin Hardener Product Part A Part B = Part C + Solvent Based Epoxies Excellent Alkali, Solvent, and Water Resistance Good Abrasion Resistance Good Acid Resistance Good Exterior Durability High Film Builds Possible in One Coat Low Temperature Application Available Dry Heat Resistance to 250 F 16
Solvent Based Epoxy Limitations Barrier Protection Only Two-Component, Limited Pot Life Chalks and Fades on Exterior Exposure Recoat Window Restrictions Solvent Odor Special Application Equipment Might be Required On the Data Page Manufacturer Certifications Available 17
Non-Slip Critical Primers Fast dry alkyds (Solvent or waterbased) Industrial acrylics (DTM) Alkyds Synthetic Resins Derived From a Reaction Between an Alcohol and an Acid. The Resins are Blended With Drying Oils and Cure by Solvent Evaporation & Oxidation Barrier and Inhibitive Protection Prone to Yellow / Saponify Traditional Versions were High in Volatile Organic Compounds (VOC) How Alkyds Cure 18
Drying Oil Amount Short Oil Alkyd Medium Oil Alkyd Long Oil Alkyd Fast Dry Aromatic Solvent Res. Poor Penetration Fast Recoatability Harder Film Quickly Embrittles Quickly Chalks Slow Dry Aliphatic Solvent Res. Penetrates Rust P P t t (2 Hrs) Long Recoat Time Softer / Pliable Film Good Exterior Durability Waterborne Acrylic Primer Single Component Water Based Fast Dry Fast Re-Coat Excellent Corrosion Protection Must Contain Inhibitors Sensitive to Temperature and Humidity During Application AND Curing (up to 30 days for cure) Industrial Acrylics Cure by Solvent Evaporation AND Coalescence Co-Solvents (coalescing solvents) act as plasticizers for acrylics. These cosolvents contribute VOC s to WB coatings. Co-solvents must remain in the film until evaporation. 19
Ambient Cure WB Acrylics O 2 Regular Acrylics Polymer after film formation before ambient cure. Primers and Topcoats Ambient Cure Acrylics Polymer chains after crosslinking at ambient temperature in the presence of atmospheric oxygen. High Performance Steel Topcoats Fluoropolymer Urethane Ambient cured Superior color and gloss retention Available in a wide range of colors Graffiti resistant t Like Liquid Kynar 20
Polysiloxane Technology High solids epoxy siloxane combines the properties of both a high performance epoxy and a polyurethane in one coat Isocyanate-free Replaces a two coat epoxy/polyurethane system alone or over zinc-rich i primer High-gloss, self-priming coating High solids, low VOC Long term color and gloss performance Corrosion and chemical resistant Outstanding application properties Polysiloxane Topcoat Polyurethanes A polyurethane coating is that derived from the reaction product of an isocyanate component and a resin blend component. Polyol + Isocyanate = Polyurethane + CO2 Good Chemical Resistance Hard, Yet Flexible Films Excellent Color and Gloss Retention Low-Temp, Formula Dependent Application No Sweat-In Time Required 21
Types of Polyurethanes Aliphatic Excellent Color Retention Excellent Gloss Retention Primarily Used as Finish Coats More Expensive than Aromatics Aromatic Yellows & Chalks in Sunlight Yellows & Chalks in Bright Artificial Light Used as Primers & Intermediate Coats Less Expensive than Aliphatics High Performance Aliphatic SSPC Paint 36 2K UV-Stable Polyurethane topcoats ASTM D4587 Level Standard of Measurement 500h Level I color change less then 2 delta E and gloss loss less then 30 units 1000h Level II ASTM D2244 & ASTM D523 2000h Level III Two component, limited pot life. Sensitive to moisture during application & cure. Aliphatic Moisture Cured Urethane Isocyanate + Humidity = Amine + CO2 Amine + Isocyanate = Polyurethane (Urea Linkage) 22
Mildew Resistant aliphatic acrylic polyurethane Excellent color and gloss retention Mildew Resistant Polyurethane High Performance Acrylics Ambient Cure Cross-linking / branching Superior Color & Gloss Retention http://www.paintsquare.com/sspcvideoproceedings/?fuseaction=view&procid=6 23
Questions? Troy Fraebel Sherwin-Williams Company 1703 Auburn Circle Lexington, KY 40505 859.552.7027 216.830.7977 efax troy.e.fraebel@sherwin.com www.sherwin-williams.com/protective 24