mechanical galvanizingTechnical DaTa SheeT

nUcOR FaSTeneR

GeneralMechanical Galvanizing is similar to Hot-Dip Galvanizing in that they both apply a thick coating of zinc metal which provides sacrificial or cathodic protection to the steel. Because zinc is more reactive than iron, the zinc galvanized coating corrodes first, protecting the steel substrate. Mechanical Galvanizing results in a very uniform coating thickness reducing thread fit issues at assembly, making it a preferable coating for structural applications. Not only does Mechanical Galvanizing provide excellent coating uniformity, but the process is consistent from batch to batch and within each batch. Consistent fastener tensioning is aided by the addition of a blue colored lubricant that is applied to all of our Mechanical Galvanized Nuts.

The Mechanical Galvanizing ProcessMechanical Galvanizing is a room temperature process in which zinc coatings are applied to fasteners without electricity (which is used for electroplating) and without heat (which is used for Hot-Dip Galvanizing). Fasteners are placed in a large rotary barrel along with zinc powder, special promoters, and glass impact media. The mechanical energy generated from the barrels rotation is transmitted through the glass impact media and causes the zinc powder to be mechanically welded to the surface of the fasteners. With a proper glass media size mix, all exposed surfaces can be coated very uniformly, and the buoyancy of the glass media cushions the fasteners in the rotating barrel to minimize thread nicking. The room temperature process ensures no chance of re-tempering or softening high strength fasteners and guards against hydrogen embrittlement because the fasteners are also never exposed to acid pickling in the process.

ApplicationMechanical Galvanizing may be specified on a wide range of structural products including ASTM A325 Structural Bolts, A563 Grade DH Heavy Hex Nuts, A307 Bolts & Studs, A449 Hex Cap Screws, F1852 Tension Control Assemblies and F436 Hardened-Steel Washers to name a few. The requirements for Mechanical Galvanizing are covered in ASTM B695, Coatings of Zinc Mechanically Deposited on Iron and Steel and are applied to a Class 55 thickness (.0022), to provide you with the corrosion protection and value you expect from Nucor products.

TDS-002A 2-15-08

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Special RequirementsMechanical Galvanizing may be applied to any A563 (AASHTO M291) Grade Nut, which are tapped oversize before galvanizing because of the ability to control the coating thickness. We have a lubricant containing a blue colored dye put on the MG coated nuts as a requirement of ASTM/AASHTO specifica-tions to prevent galling during assembly. The visible dye is a requirement to enable visual confirmation of the presence of a lubricant. The blue color of Nucor Fasteners Mechanical Galvanized nuts distinguishes them from our green dye lubricated Hot Dip Galvanized nuts to help prevent mixing. There shall be no mixed coating types on structural bolt/nut combinations per the specifications.

Testing/Certification RequirementsOur domestic sources for Mechanical Galvanizing are qualified and utilize in-process quality systems enabling us to maintain full traceability from raw material to each container of product we ship. Chemical and physical certifications are provided with every shipment. Nucor Fastener is TS16949 & ISO9001 Registered and our laboratory is A2LA Accredited. ASTM A490, ASTM A490M and ASTM F2280 Structural Products are not permitted to be Mechanical Galvanized.

ASTM B695 AASHTO M298

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This Technical Data Sheet is subject to change without prior notification.

TODAY, THAT LITTLE n MEANS BIG THINGS!

COATING MINIMUM THICKNESS MINIMUM SALT SPRAY

CLASS (UM) (IN.) (HRS. TO RED RUST)

110 107 .0043 NOT SPECIFIED

80 81 .0032 NOT SPECIFIED

70 69 .0028 NOT SPECIFIED

65 66 .0026 NOT SPECIFIED

55 53 .0022 NOT SPECIFIED

50 50 .0020 300

40 40 .0016 250

25 25 .0010 192

12 12 .0005 96

8 8 .0003 56

5 5 .0002 36