GALVANISING

For use in construction at coastal areas it shall be required for galvanizing the

Cross arms and Pole top brackets as following :

All galvanizing shall be carried out by the hot dip process, in accordance with

Specification IS 2629. However, high tensile steel nuts, bolts and spring washer

shall be electro galvanized to Service Condition 4. The zinc coating shall be

smooth, continuous and uniform. It shall be free from acid spot and shall not

scale, blister or be removable by handling or packing. There shall be no impurities

in the zinc or additives to the galvanic bath which could have a detrimental effect

on the durability of the zinc coating.

Before picking, all welding, drilling, cutting, grinding and other finishing

operations must be completed and all grease, paints, varnish, oil, welding slag and

other foreign matter completely removed. All protuberances which would affect

the life of galvanizing shall also be removed.

The weight of zinc deposited shall be in accordance with that stated in

Standard IS 2629 and shall not less than 0.61kg/m² with a minimum

thickness of 86 microns for items of thickness more than 5mm, 0.46kg/m² (64

microns) for items of thickness between 2mm and 5mm and 0.33kg/m² (47

microns) for items less than 2mm thick.

Parts shall not be galvanized if their shapes are such that the pickling solutions

cannot be removed with certainty or if galvanizing would be unsatisfactory or if

their mechanical strength would be reduced. Surfaces in contact with oil shall not

be galvanized unless they are subsequently coated with an oil resistant varnish or

paint.

In the event of damage to the galvanizing the method used for repair shall be

subject to the approval of the Project Manager or that of his representative.

Repair of galvanizing on site will generally not be permitted.

The threads of all galvanized bolts and screwed rods shall be cleared of spelter by

spinning or brushing. A die shall not be used for cleaning the threads unless

specifically approved by the Project Manager. All nuts shall be galvanized. The

threads of nuts shall be cleaned with a tap and the threads oiled.

Partial immersion of the work shall not be permitted and the galvanizing tank

must therefore be sufficiently large to permit galvanizing to be carried out by one

immersion.

After galvanizing no drilling or welding shall be performed on the galvanized

parts of the equipment excepting that nuts may be threaded after galvanizing. To

avoid the formation of white rust galvanized materials shall be stacked during

transport and stored in such a manner as to permit adequate ventilation. Sodium

dichromate treatment shall be provided to avoid formation of white rust after hot

dip galvanization.

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