UL 5:2016 pdf free download – STANDARD FOR SAFETY Surface Metal Raceways and Fittings.
13 Corrosion Protection
13.1 General
13.1.1 Metal raceway and fittings shall be protected against corrosion on all inside and outside surfaces in accordance with 13.2 or 13.3 or the metal shall have been evaluated and determined to be inherently resistant to ordinary dry-locations indoor atmospheric corrosion. Such protection is not required on cut edges. Where spot welds are made on metallic material the integrity of the coating shall be maintained.
13.2 Zinc coatings
13.2.1 A zinc coating shall cover a raceway or fitting part completely, adhere firmly at all points, be smooth and free from blisters or other defects that lessen the protective value, be in metal-to-metal contact with the ferrous metal, and be evenly distributed on each surface of the finished part. A zinc coating on an interior surface shall not have an average thickness of less than 0.00015 inch (0.0038 mm) nor a minimum thickness less than 0.0001 inch (0.0025 mm). A zinc coating on an exterior surface shall not have an average thickness less than 0.0005 inch (0.013 mm) nor a minimum thickness less than 0.0004 inch (0.0102 mm). Any applicable method of determining the thickness of the zinc is satisfactory. When the results of any measurement are in doubt, the results of measurement by means of the test described in 17.1 — 17.10 are to be taken as conclusive.
Exception: The zinc coating on the broad faces of a part that is formed from hot-dip-mill-galvanized steel sheet or coil is acceptable without investigation when both of the following apply to the unformed sheet or coil:
a) The sheet or coil comes from the steel mill with either of the standard surface markings “G60” or “A60 ,“ or with a proprietary coating identification. Large coils that are not surface
marked shall have the “G60” or “A 60 ,“ or the proprietary coating identification, marked on the mill certificate. These markings indicate that the zinc coating is designated G60 or A60 in
conformance with Table 1 of the Standard Specification for Steel Sheet, Zinc-Coated
(Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process, ASTM A 653/ A653M, or has been determined to be equivalent to a standard G60 or A60 coating.
b) Not less than 40 percent of the zinc is on any one side of the sheet or coil based on the
minimum single-spot-test check-limit total for both sides of the sheet or coil of 0.50 oz/ft2 (152 g/m2) specified in ASTM A653/A653M. The method of determining the weight of zinc coating per unit area (sum of the weights of coating on both sides of the sheet or coil) is to be any
applicable method. However, in cases where the results of any measurement are in doubt, the results of measurements by means of the standard method or standard alternative method for galvanized sheets (coils included) described in the Standard Test Methods for Weight [Mass] of Coating on Iron and Steel Articles with Zinc or Zinc Alloy Coatings, ASTM A90, are to be taken as conclusive.
13.2.2 An annealed zinc coating (A60 or its proprietary equivalent included, G60 or its proprietary equivalent excluded) on steel sheet or coil that is bent, extruded, rolled, or otherwise formed after annealing, is to be considered damaged and not in compliance with the requirements when flaking or cracking of the zinc is visible under 25-power magnification at the outside radius of the formed area unless additionally nonmetallic-coated in the formed area.