ZINC COATINGS ON IRON, STEEL, AND FASTENERS
This IM covers the requirements of zinc coating (galvanizing) by the hot dip and mechanically deposited processes on iron and steel products.
The following items shall be furnished only from approved galvanizers identified in the Materials Approved Products Listing Enterprise (MAPLE):
1. Iron or steel items specifically fabricated for Iowa projects
2. Anchor Bolts and Swedge anchor bolts
When galvanizer approval is required, the galvanizers shall be approved prior to galvanizing any steel products or fabricated items for use on Iowa Department of Transportation projects.
Galvanizing companies seeking approval shall provide the Office of Construction and Materials the following information either in the Company’s written Quality Control Plan or as separate documentation:
1. Name and location of the galvanizing plant
2. Identification of any of the following ASTM specifications for which the galvanizing plant has routine experience:
ASTM A-53
ASTM A-123
ASTM B- 695
ASTM F-2329
3. Galvanizing Tank(s) dimensions
4. Molten Zinc
4.1. Composition (Percent by weight)
4.2. Temperature Control and high / low temperature range
4.3. Special Temperature Control for Compliance with ASTM F- 2329
5. Preparation and Q/C procedures prior to galvanizing items
6. Post-galvanizing treatments
7. Post-galvanizing Q/C procedures
7.1. Coating thickness measurement procedures
7.2. Special inspection of surfaces for items intended to receive paint over galvanizing
8. Preparation for Shipment with emphasis on protection of the galvanized coating during handling and transportation.
9. Sample of the company’s galvanizing certification documentation
Note; The Iowa Department of Transportation does not accept certification to dual standards such as ASTM A-153/ F2329.
HOT DIP GALVANIZED COATINGS ON IRON AND STEEL PRODUCT
For determining coating thickness grade per ASTM A123, use the following definitions:
Structural shapes – as defined by the American Institute of Steel Construction (AISC) Steel Construction Manual. Examples include but are not limited to: Angles, Channels and W shapes.
Strip and Bar – 8 in. or less in width per AISC Steel Construction Manual
Plate – over 8 in. in width per AISC Steel Construction Manual. Includes bent plates.
Pipe and Tubing – Includes pipe (unfilled), square and rectangular tubing.
All sharp edges shall be rounded up (to near 1/16”) prior to galvanizing.
High spots and rough edges such as the metal drip line shall be removed until it is level with the surrounding area, taking care that the base coating is not removed.
The zinc coating thickness shall be uniform inside and outside of pipes, tubes, poles and/or certain tanks.
A chromate treatment is given to galvanized products which are used in fresh concrete to prevent a reaction between the galvanizing and the fresh Portland cement paste. The chromate treatment shall be performed immediately after the galvanizing process.
TRAVEL LOG
A travel log shall be required for every project with paint or powder coating over galvanizing and shall be initiated by the steel fabricator.
A copy of the travel log is attached to IM 557, Appendix H.
The travel log shall accompany the fabricated items to be galvanized. The galvanizer shall be required to complete the Galvanizer portion of the travel log and indicate the type of treatment (if any), that has been performed on the galvanized item, the date of galvanizing, signature and date.
No preparation or galvanizing of items to be painted or powder coated may be performed without a travel log from the steel fabricator.
Fasteners can only be galvanized by either of these two processes: Mechanically galvanized to ASTM B 695 Class 55 or hot dip galvanized to the requirements of ASTM F 2329.
All threaded components (bolts, nuts, and anchor bolts) shall be coated by the same zinc coating process. No mixed processes in a lot shall be allowed.
The maximum temperature of hot bath cannot exceed 850º F. Galvanizing carried out at a temperature above 850º F can adversely affect the final mechanical properties of fasteners.
Dual zinc certifications such as A153/F2329 shall not be acceptable and shall be grounds for rejection.
Articles and fasteners that are galvanized shall be protected from any damage to the coating, surface finish and appearance.
Fasteners shall be transported in weather tight containers
Bridge Components and Miscellaneous Items:
1. Items shall be transported and stored under dry and well ventilated conditions to avoid wet storage staining.
2. When stored outdoors or transported, surface to surface contact between items shall be avoided with suitable packing material between galvanized items.
3. When stored outside, items shall be stored off the ground and when possible, at a slight angle to allow water to run off.
4. Suitable packing shall be placed between layers of stacked or bundled galvanized items.
5. Suitable packing materials may be foam padding, foam wrap, carpet or cardboard. It shall be placed between layers of stacked or bundled items before binding them together
The galvanizer shall certify to the state of Iowa that the samples representing each lot have been tested and inspected as required by the intended specification and that the requirements have been met. The galvanizer shall furnish on each shipment day a certified bill of materials or invoice, which identifies the county, project number, contractor’s name and the number of coated items. Additionally, the galvanizer shall report the average galvanizing temperature and the average coating thickness of the production lot shall be furnished.
The certification of compliance shall be signed by a designated or responsible company representative and shall be stated as follows:
The materials itemized in this shipment are certified to be in compliance with the applicable ASTM Standards and the Iowa Department of Transportation Standard Specifications, IMs and meet the Buy America requirements as described in IM 107 for all steel, iron products and coatings.
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ACCEPTANCE
All galvanized items require a signed certification statement
For items described in the General section of this IM, the following are required:
· Approved galvanizer
· Thickness test report
Refer to IM 453.06B for High Strength / Non-high Strength fastener requirements
As a coating, the zinc material is not required to be from a domestic source but it must be applied in the USA to meet the Buy America requirements.