Corrkil

As per clause39.2.2 of IRS-B1for locations where girders are exposed to corrosive environment i.e. flooring system of open web girders in all cases, girders in industrial, suburban or coastal areas etc., protective coating by metalizing followed by painting as mentioned in clause 39.2.1 or by painting using epoxy based paints as per the following painting schedule may be applied

 

1. Surface Preparation

 

a) Remove oil/grease from the metal surface by using petroleum hydrocarbon solvent to IS: 1745.

b) Prepare the surface by sand or grit blasting to Sa 2-1/2 to IS: 9954 i.e. near white metallic surface.

 

2. Painting

 

(a) Primer Coat - Apply by brush/airless spray two coats of Epoxy

Zinc Phosphate primer to RDSO Specification No. M&C/PCN/102/86 to 60 microns min, dry film thickness(DFT) giving sufficient time gap

between two coats to enable the first coat of primer to hard dry.

 

(b) Intermediate Coat Apply by brush/ airless spray one coat of Epoxy Micaceous Iron Oxide paint to RDSO Specification No. M&C/PCN/ 103/86 to 100 microns minimum DFT of 100 and allow it to hard dry.

 

(c) Finishing Coat Apply by brush/airless spray two coats of polyurethane aluminium finishing to RDSO Specification No. M&C/PCN- 110/88 for coastal locations or polyurethane red oxide (red oxide to 150 446 as per 15:5) to RDSO Specification M&C/PCN-109/88 for other locations to 40 microns minimum DFT giving sufficient time gap between two coats to enable the first coat to hard dry.

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2. Surface preparation

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Remove the thick scales of rust on the metal sarface with mild hammer strukes and clean out the surface dioroughly by scratching with metal sharpnels and sisel-wire brushes. Then remove the loose rest particles on the metal surface by rubbing with dry cloth Remove the stains of grease or oils on the rectal surface by cleaning with kerosene. Make sure that the cleaned metal surface is completely dy before application.

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3. Paint application

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On the dean and dry metal surface, give a coating of Zinc Phosplute/Zinc Gliromate Primer and allow to dry for one day (DFT 30-50 micron).

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After shaking the compound very well give two even coatings of the material with nylon brushes, each coating at an inrerval of one day while giving the coatings, do not unduly rub the brush for a long time over the same spot. The surface of the coating becomes tack-free within six hours and dries up completely within 24 hours. Total hard drying through complete cross linkages of the co polymer takes about a week. The total dry film thickness with two coals of paint and one coat of primer should not be less than 140 microns. The finishing coats are to be applied in shop and touched after erection if necessary.