UL 5:2009 pdf download – Surface Metal Raceways and Fittings.
9 Corrosion Protection
9.1 General
9,1.1 Metal raceway and fittings shall be protected against corrosion on all inside and outside surfaces in accordance with 9.2 or 9.3 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.
9.2 Zinc coatings
9.2.1 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 metalto-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 11.1 — 11.10 are to be taken as conclusive.
Exception: The zinc coating on the broad laces of a part that is formed from hot-dip-miP-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 ‘G6c or ‘460, or with a proprietary coating identification. Large coils that are not surface marked shall have the ‘G6(r or A6O.’ or the propnetary coaling 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 lou- Steel Sheet, Zinc-Coated (Ciatvan,zed) or Zinc-Iron Alloy-Coaled (Galvannealed) by the Hot-Oip Process. ASTM A653, 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 sin gte-spot ‘test check-limit total for both sides of the sheet or coil of 0.51L) ozfft2 (152 g/m2) specified in ASTM A653. 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.
9.2.2 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.
9.2.3 Steel sheet or coil which has an annealed zinc coating and is sheared, cut, or punched to result in a hole or an edge (straight or other) without also being formed at the edge or hole, is not required to have protection added at the edge or hole. However, in cases where the metal is formed at the edge or hole and the examination under magnification reveals damage to the zinc (see 9.2.2), added protection shall cover the damaged area.