7-176 Section 716. Shop Cleaning a nd Coating Structural Steel
716.01 Description
This work consists of shop cleaning and applying a complete coating system on new structural steel as a part of fabricating and providing structural steel; field cleaning and repairing surfaces damaged in shipping, handling, and erecting the structural steel; and repairing damaged galvanized surfaces. Refer to SSPC Painting Manual , Volumes 1 and 2, for definitions of cleaning criteria and ot her coating terms. If more than 500 square feet of steel surface is to be coated, the work must be performed by a fabricator with an AISC Sophisticated Paint Endorsement . SSPC QP 3, Certification Standard for Shop Application of Complex Protective Systems, will also be accepted.
716.02 Materials
Provide materials in accordance with the following sections : Sealant for Perimeter of Beam Plates ................................................... 713 Bridge Coating System ......................................................................... 915 Provide materials in accordance with subsection 715.02. Steel shot is allowed for shop cleaning of structural steel.
716.03 Construction
A.Cleaning Structural Steel . Before cleaning, remove oil or grease deposits in accordance with SSPC -SP 1, Solvent Cleaning. Clean surfaces to SSPC -SP 10, Near White Blast Cleaning . Grind surface irregularities, including fins, tears, slivers, and burred or sharp edges on steel members in accordance with SSPC -SP 11, Bare Metal Power Tool Cleaning. The Engineer will inspect for steel cleanliness using the visual standard specified in SSPC -VIS 1 , Guide and Reference Photographs for Steel Surfaces Prepared by Dry Abrasive Blast Cleaning, and SSPC -SP 10 for the initial rust condition. Remove abrasives from steel surfaces with a commercial -grade vacuum cleaner equipped with a brush -type cleaning tool or by double blowing with partial vacuuming. If using the double blowing method, vacuum the top surfaces of structural steel, including flanges, longitudinal stiffeners, splice plates, and hangers after double blowing. For blowing the steel clean, use an air line with an in-line water trap that delivers compressed air free of oil and water as it leaves the air -line. Maintain steel dust free and prime within 8 hours of cleaning. MDOT Standard Specifications for Construction Section 716 7-177 Before shop coating, mask areas requiring field welding, except top flange areas receiving welded shear developers . After applying the prime coat, but before applying the intermediate coat, mask areas where welding shear developers to the top flange.
B.Coating Structural Steel . Load material for shipment after the shop coating has cured and the Engineer has inspected the material . The Engineer will stamp the components “Recommended for Use” after loading is complete if they satisfy the contract .
1.Applying the Coating . Coat structural steel in accordance with subsection 715.03.D.1 and subsection 715.03.D.3, except p rovide a primer DFT for the top flange between 4. 0 and 8.0 mils.
2.Coating Faying Surfaces and Connections. Faying surfaces are all surfaces internal to a connection that bear on an adjacent surface including the contact surfac e of bolts, nuts, and washers . Before cleaning and coating, disassemble bolted connections . Blast clean components separately . Apply a prime coat and allow to cure before reassembly . Use the same primer for both connecting surfaces . Vacuum the connection a gain immediately before reassembly . If the Engineer determines that the surface is not clean enough for bolting, scrub the surface with a commercial detergent and rinse with water before assembling the connection. Reassemble the connection by tightening the bolts using the turn-of -nut method in accordance with subsection 707.03. E.6.d.
a.Slip Critical Connections . Apply the same primer to faying surfaces and filler plate surfaces . Apply prime coat to a minimum DFT of 1.0 mil and a maximum DFT determined by the slip coefficient test results in accordance with subsection 715 .02. Apply a prime coat to the external surfaces of splice plates with a DFT from 4 .0 to 10.0 mils. The primer must meet the requirements of Class B slip coefficient . Mask the faying surface during subsequent coat applications.
b.Other Connections . Apply the same prime coat to faying surfaces, other than slip critical surfaces , in accordance with subsection 715.03.D.1. Mask t he faying surface before subsequent shop coating operations . After assembly in the field, solvent -clean exposed primed splices and other bolted connection locations in accordance with SSPC -SP 1 . Use the same intermediate and top coat materials as for the r emainder of the structure . Apply an intermediate and top coat to exposed surfaces of the bolts, nuts, and washers in accordance with subsection
715.03 D.1.
MDOT Standard Specifications for Construction Section 716 7-178 c. Contact Surfaces without Primer . If painting with an epoxy intermediate coat, edge seal unprimed contact surfaces . Use a sealant designated for sealing perimeter of beam repairs selected from the Qualified Products List.
3.Stenciling . Apply stencils in accordance with subsection 715.03.D.5. Designate the coating type as 4S.
4.Galvanizing . When required by the contract, or as a substitute for applying a zinc -rich primer , hot-dipped galvanizing of structural steel members in accordance with A ASHTO M111 M/M111 will be allowed , except for surfaces internal to slip critical connections and surfaces of filler plates . Apply a zinc -rich primer to coat surfaces internal to slip critical connections and surfaces of filler plates at a minimum DFT of 1.0 mil and a maximum DFT as determined by the slip coefficient test results in accordance with subsection 715 .02. Mask the faying surface before applying subsequent coats . Apply subsequent coats in accordance with subsection 715.03.D . Repair damaged galvanized surface in accordance with subsection 716.03.E. Galvanize portions of bearings not welded to the structure and other structural steel required to be galvanized in accordance with AASHTO M111 M/M111 . Remove weld spatter by grinding before galvanizing. In addition, remove mill scale and welding slag by abrasive blasting before galvanizing. Prepare steel components for galvanizing in accordance with SSPC -SP 8, Pickling . Perform galvanizing using the “dry process. ” Do not quench the galvanized components after galvanizing. If the contract requires a top coat on galvanized components, do not apply a chromate surface passivation. Apply a galvanizing thickness of at least 3.9 mils or 2.3 ounces per square foot. Areas of field connections must have a uniform galvanized coating thickness, free of local excessive roughness that prevents splice plates , bearings, or other field connections from making full contact. In the shop after galvanizing, use a hand wire brush to roughen faying surfaces other than slip critical connections . Do not use powered wire brushes . Field splice bolt holes must be free of zinc buildup. Check each hole in the shop after galvanizing to verify that the hole is able to receive a drift or barrel pin with a diameter of 1⁄16 inch plus the diameter of the bolt. After galvanizing, place structural steel in a second shop assembly in accordance with subsection 707.03. D.14 to check alignment of holes, MDOT Standard Specifications for Construction Section 716 7-179 sweep, and camber against the fabricator ’s original recorded lay down dimensions . The fabricator ’s personnel may perform this shop assembly at the galvanizer ’s facility if approved by the Engineer . The Engineer may waive the second shop assembly if the fabricator records individual beam or girder cambers and sweeps during the first shop assembly and the dimensions after galvanizing fall within the following tolerances:
a.Bearing points after galvanizing are ±⅛ inch from the first shop assembly;
b.Camber points after galvanizing are +¼ inch or −0 inch from the first shop assembly ; and
c.Sweep points after galvanizing are ±⅜ inch from the first shop assembly . If individual beams or girders exceed the listed tolerances, place the beam or girder with at least two adjacent beams or girders in the shop assembly to check against the recorded shop assembly records in accordance with subsection 707.03. D.7. The fabricator will record, and the Engineer will witness, the second shop assembly or individual member cambers. For galvanized elements required to be painted, prepare the surface in accordance with ASTM D6386 prior to painting, except remove zinc high spots including, but not limited to, bumps, runs, drips, and dross inclusions on galvanized steel members by grinding or filing until they are level with the surrounding area. SSPC -SP 16, Brush -off Blast Cleaning of Non-Ferrous Metals , must be used when sweep blasting for surface preparation prior to coating, except the minimum surface profile must to be 1.0 mil. After cleaning, inspect the surface for conformance with the required zinc thickness in accordance with galvanizing specifications. Stencil in accordance with subsection 715.03.D.5 except designate the coating type as 4GS.
C.Handling Coated Steel . Use care when handling coated steel in the shop and during shipment, erection, and assembly . Do not move or handle coated steel until the coating cures . Protect the steel from binding chains with softeners approved by the Engineer . Use padded hooks and slings to hoist steel . Space diaphragms and similar pieces during shipment to prevent damage from rubbing. At the project site, store the steel components on pallets so they are not in contact with the ground or fall against or rest on each other . Provide shipping and project storage details MDOT Standard Specifications for Construction Section 716 7-180 to the Engineer at the pre-fabrication meeting and obtain the Engineer ’s approval before shipping the steel.
D.Shop and Field Repair . Make shop and field repairs to the coating in accordance with the coating manufacturer ’s recommendations or in accordance with this section, whichever i s more stringent . Submit written procedures to the Engineer and obtain the Engineer ’s approval for shop and field repairs for approval before applying coating. For surfaces, inaccessible after erection, repair and recoat before erection. Prepare accessible steel for repairs after completion of erection work, including connections and straightening of bent steel.
1.Cleaning . Shop clean in accordance with subsection 716.03.A . Field clean in accordance with subsection 715.03.C.
2.Coating . Apply shop coats in accor dance with subsection 716.03.B . Apply field coats in accordance with subsection 715.03.D, using the same coating material as applied in the shop.
E.Repair of Damaged Galvanized Surfaces. If damage occurs to the z inc coating during transporting, handling, or installing, repair the damage at no additional cost to the Department . Exposed underlying steel or coating thickness less than 50% of the specified thickness or thickness equivalent is considered damage. Thickness equivalent is 1 ounce of zinc per square foot equals 1.7 mils. For repair coating, apply a coating 1.5 times the thickness or thickness equivalent specified for galvanizing on the item but not less than 5 mils. Use zinc -based solder, zinc -rich primer , or zinc metallizing in accordance with ASTM A780 /A780M . Obtain the Engineer ’s approval before using zinc metalizing . Clean the metal and apply the coating in accordance with A nnex A1, A2, or A3 of ASTM A780 /A780M , except as modified in this subsection. If using zinc -based solder for repair, use temperature-sensitive crayons to verify the preheat temperature of the metal before depositing the zinc alloy. If using zinc -rich prime r for repair, clean the damaged surface to near-white metal before applying the primer . Apply the primer in accordance with the manufacturer ’s recommendations for temperature and dryness.
716.04 Measurement and Payment
Pay Item Pay Unit Field Repr of Damaged Coat ing (Structure Identification) ............... Lump Sum MDOT Standard Specifications for Construction Section 716 7-181 The Engineer will measure Field Repr of Damaged Coating (Structure Identification) as a unit for each structure . The unit price for Field Repr of Damaged Coating (Structure Identification) includes the costs of making field repairs to the previously applied coating system; prime coat ing surfaces and exposed surfaces of bolts, nuts, and washers; and repairing stenciling and the coating of galvanized components that are not shop coated. The unit price for Structural Steel, Furn and Fab of the type specified includes the cost of applyi ng and shop repairing the complete coating system, including stenciling and approved sealants. Repair of damaged galvanized surfaces is included in the pay item for furnishing the galvanized component.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 540–545 of 1,146.