Zinc Coating Standards Electro-Galvanisation vs Hot Dipped Galvanisation

[PeterMcGonigleCRH]

Hi All,

I am currently designing coiled roofing nails. I have carried out some research and found out for Hot Dipped galvanisation:

According to the standard: ASTM A 153/A 153 M-09 the zinc coating for fasteners under 9.52mm in diameter are:

• Average Mass: 305 g/m2 - Any Individual specimen: 259 g/m2 (Midpoint value is 281.5g/m2)
• Average Thickness: 43 microns - Any Individual specimen: 36 microns

I have put this to the supplier for the coiled roofing nails and they say that coiled roofing nails are galvanized using the Electro-galvanisation process and that the Zinc coating for Electro-Galvaisation is normally 2-5microns.

This seems like a huge difference in coating thickness between the two processes.

has anyone any advice on how to proceed?

 

[CoryPad]

Electro-galvanization is usually called electroplating in English. A typical standard would be ASTM B633 Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel. The lowest performance coating in ASTM B633 is SC 1, with a minimum thickness of 5 micrometers. Coiled roofing nails are available with both types of coatings, see here:

http://www.grip-rite.com/us/en/products/collated-fasteners/roofing/15d-wire-weld-coil-roofing-nails

Obvious hot dipped galvanizing offers higher performance for more extreme conditions, at a higher price. You will need to determine what is needed for your application. In general, a steel nail with 2 micrometers of zinc plating will become covered with red rust in a few years if exposed to substantial corrosivity (e.g. salt spray mist in a coastal location).