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August 6, 201

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• Abrasion Resistance: As mentioned above, the hot-dip galvanizing process creates a metallurgical bond to the steel substrate, which forms zinc-iron alloy layers. See photomicrograph of batch hot-dip galvanized coating below. The iron/zinc alloy layers become harder (DPN hardness) with increasing iron content; to the point that the inner alloy layers are harder than that of the base steel. This is critical for helical anchors and piles since the coating must be both flexible and hard to stand up to the abrasion during installation. Materials plated per ASTM B633 have a thin layer of pure zinc on the surface. The pure zinc has a hardness of about 1/3 - 1/2 that of the base steel.

• Coverage of the Protective Coating: Hot-dip galvanizing is a total immersion process, therefore all

surfaces will be completely protected. The application of the zinc plating per ASTM B633 is limited by the level of expertise of the individual doing the application. Because of this, there is a potential that “hard to reach places” may not be adequately protected.

Most of the information contained in this letter was obtained from various publications by the American Galvanizers Association (AGA). Additional information can be found on their website: www.galvanizeit.org . Also included below are figures showing the relative thickness of various zinc coatings and a photomicrograph of a hot-dipped galvanized coating. Lab Tests: Salt fog tests per ASTM B117 can be used to conduct continuous salt spray testing to provide a very useful method for undertaking comparative testing. This procedure is also known as 'ranking'. Such tests work on the basis of comparing actual corrosion rates with expected corrosion rates which are based on previous

experience, in a practical application situation. For this reason, continuous salt spray testing is most often carried out as a quality audit function to assess a production process, or viability of a particular product or material. Two component parts from two foundation repair brackets were tested in a salt fog chamber at the same time. One component was hot-dip galvanized per ASTM A153 Class B and the other component was plated per ASTM B633. The samples were placed in the Salt Fog chamber suspended on non-metallic supports. The samples were left in the salt fog chamber for 1040 hours (43.3 days). The photos below show the results. The hot-dip galvanized part is covered in salt residue, and shows a few points of rust penetration. By contrast, the plated part is fully covered in thick, red rust.

Hot-Dip Galvanized (1040 Hours) Plated (1040 Hours) The salt fog test data clearly demonstrates that hot-dip galvanized coatings are superior for corrosion protection when compared to zinc plated coatings. To conclude, Hubbell / CHANCE does not recommend zinc plating per ASTM B633 for helical anchors and piles. There is a clear difference and the better choice is hot-dip galvanizing. If you have any questions or require any additional clarification or information, please do not hesitate to contact me. Sincerely,

Gary L. Seider, P.E. Civil and Utility Helical Products Hubbell Power Systems, Inc. / CHANCE