BS ISO 8179-1:2017 pdf download – Ductile iron pipes, fittings, accessories and their joints — External zinc-based coating Part 1: Metallic zinc with finishing layer 5 Zinc-based coating 5.1 Pipeline component surface condition The pipeline component surface shall be dry and free from rust and any non-adhering particles or foreign matter such as oil or grease. The metallic zinc-based coating shall be applied to the as-cast annealed external surface of the pipeline component, or to a blast-cleaned or ground surface at the manufacturer’s discretion. 5.2 Method of application The metallic zinc-based coating shall be applied by a spraying process in which metallic zinc or zinc alloy is heated to a molten state and projected in small droplets by spray guns on to the pipeline component surface. The design and construction of the spray equipment are not within the scope of this document. 5.3 Coating characteristics The metallic zinc-based coating shall cover the outside surface of the pipeline component and shall be free from such defects as bare patches or lack of adhesion. A spiralled appearance is permissible provided that the zinc-based coating masses comply with the requirements of5.4. The manufacturer shall define those coating irregularities which are considered not detrimental to the performance of the coating system. Damaged areas of zinc-based coating caused by handling are acceptable, provided that the area of damage is less than 5 cm 2 per square metre and that the minor dimension of the damaged area does not exceed 5 mm. Greater areas of damage shall be repaired in accordance with 5.5. 5.4 Zinc-based coating mass The mean mass of zinc-based coating measured in accordance with7.1 shall be as follows: — not less than 200 g/m 2 with a local minimum of 180 g/m 2 ; — in low corrosive areas, by agreement between the purchaser and the supplier, 130 g/m 2 of zinc with a local minimum of 110 g/m 2 ; — in case of very corrosive soils, the manufacturer and the purchaser may decide to use additional coating mass. The manufacturer shall visually inspect each pipeline component for quality and uniformity of coating and shall carry out regular measurements of zinc-based coating masses in accordance with the method described in 7.1. The factory quality control tests ensure conformity to the standard. Factory quality control tests shall be the sole determinant of coating thickness acceptance. Where informative field verification is required, one of...
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