ISO 8179-2:1995 pdf free download.Ductile iron pipes – External zinc coating – Part 2 : Zinc rich paint with finishing layer.
1 Scope
This part of ISO 8179 deals with a factory-applied protective external coating system for centrifugally cast ductile iron pipes as specified in ISO 2531 and ISO 7186. This coating system comprises a metallic zinc layer followed by a finishing layer.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO 8179. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 8179 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain rogistors of currontly valid Intornational Standards.
ISO 2531:1991, Ductile iron pipes, fittings and accessories for pressure pipe-lines.
ISO 7186:1983, Ductile iron pipes and accessories for non-pressure pipe-lines.
3 Materials
The coating materials are zinc rich paint with inorganic binder and a zinc content of at least 85 % (rn/rn) in the dry film, and bituminous paint or synthetic resin compatible with zinc rich paint.
4 Zinc rich paint coating
4.1 Pipe surface condition
The pipe surface shaH be dry and free from rust or any non-adhering particles or foreign matter such as oil or grease.
The zinc shall be applied to the oxidized external surface of the pipe, or to a blast-cleaned or ground surface, at the manufacturer’s discretion.
4.2 Method of application
The zinc rich paint coating shall be applied by a spraying or a brushing process on to the pipe surface.
The design and Construction of the coating equipment is not within the scope of this part of ISO 8179.
4.3 Coating characteristics
The zinc rich paint coating shall coer the out&de diameter of the pipe, and shall be free from such defects as bare patches or lack of adhesion.
A spiralled appearance is permissible provided that the zinc rich paint coating masses comply with the requirements of 4.4.
Damaged areas of zinc rich paint coating caused by handling are acceptable, provided that the area of damage is less than 5 cm2 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 4.6
4.4 Zinc rich paint mass
The mean mass of zinc rich paint coating measured in accordance with 4.5 shall be not less than 150 g/m2, with a local minimum of 130 g/m2.
The manufacturer shall visually inspect each pipe for quality and uniformity of coating and shall carry out regular measurements of zinc rich paint coating massAs in arr.nrdancp with th mthnd dPscrihAd in
4.5.
4.5 Determination of zinc rich paint coating mass
A rectangular token is attached along the pipe axis before passing it through the zinc rich paint coating equipment. After coating and trimming, the minimum token sires shall be either
a) 250mmxl0Ommor
b) 500mmxSOmm.
The mean mass of zinc rich paint coating, m, expressed in grams per square metre, is calculated from tho mass difforonco of tho token bofore arid after zinc rich paint coating using the following formula:where
m1 and ni2 are masses, in grams, before and after zinc coating, measured to an accuracy of 0,1 g;
A is the area of the token, in square metres;
C is a correction factor depending on the material of the token, taking into account the difference in surface roughness between the token and the pipe surface.
The value of C shall be determined by the manufacturer and specified when required in test documents.
NOTE 1 For information, C lies between 1.0 and 1.2 for sand-blasted steel sheet or polyester sheet.
m2 should be measured after the sample has been dried
The uniformity of the zinc rich paint coating is checked by visual inspection of the token. In the event of lack of uniformity, pieces 50 mm x 50 mm shall be Cut from the token in the lighter zones and the local minimum mass of zinc rich paint coating determined according to the above method.
4.6 Repairs to the zinc rich paint coating
The manufacturer is permitted to carry out repairs by zinc rich paint coating, provided that the requirements of clause 3, and subclauses 4.3 and 4.4 are met.
5 Finishing layer
After zinc rich paint coating, the pipe shall be given a finishing layer of bituminous paint or synthetic resin compatible with the zinc rich paint coating.
Application of this finishing layer may be done by any proven process such as spraying or brush coating at the manufacturer’s discretion. It shall uniformly cover the zinc rich paint coating and be free from bare patches or lack of adhesion.
The mean dry film thickness of the finishing layer shall be not less than 70 im with a local minimum thickness of 50 rim.
Verification of the dry film thickness of the finishing layer shall be carried out by measurement
a) directly on the pipes by means of suitable gauges, e.g. magnetic. or by using a “wet film U thickness gauge where a correlation between wet film thickness and dry film thickness can be demonstrated or
b) indirectly on a sample token which is attached to the pipe before coating and is used after coating to measure the dry film thickness by appropriate means, e.g. micrometer, magnetic thickness gauge or by a weight method similar to 4.5
NOTE 2 The method of measurement is at the manufacturer’s discretion.