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HOW TO USE Locate your project on the map
THE ZINC MILLENNIUM MAP Annual Average Atmospheric Corrosion of Zinc, UK and Republic of Ireland, 1998-2000
Match the colour of the square to the key Read off the average background corrosion rate in lum per annum
Identify the minimum average galvanized coating thickness for steelwork in lum
Divide the coating thickness
(average 85 lum) by the corrosion rate to obtain the expected minimum life of the galvanized coating.
This is an approximate guide and is most relevant to static, exterior- exposed structures. Specifiers will need to take account of any site specific factors which may affect the corrosion rate.
Detailed data for individual sites and advice on its interpretation (e.g. the possible effects of a local micro- climate on the corrosion rate actually experienced by the galvanized structure) is available from Galvanizers Association.
ZINC CORROSION RATES
Zinc corrosion rates are represented by five categories indicated by the colour codes shown below.
Corrosion Category 12 3
Average Corrosion rate (lum/year)
Average life of 85 lum galvanized coating
(years) 4 5 0.5 1 1.5 2 2.5 170 85 57 43 34 ACKNOWLEDGMENTS
- Agricultural Development Advisory Service (ADAS Consulting) for project management. - Mr Tom Shaw for consultancy services throughout the project and for application of the Thiessen method to the project data.
- Britannia Zinc Limited for provision of laboratory facilities. - Mr John Curtain (consultant) and Mr Michael Taylor (Britannia Zinc Limited) for valuable project assistance.
- All those who provided sample sites for the project.
Cartographic reproduction by Lovell Johns Ltd, Copyright: Galvanizers Association 2001. Based upon the Ordnance Survey 1:1,500,000 map, with the permission of the controller of The Stationary Office.
ADAS Consulting and GA are grateful to Orange Plc for provision of survey sites in the UK and the Irish Electricity Supply Board for survey sites that allowed corrosion rates at key Irish locations to be included in the Zinc Millennium Map. Further studies are planned to extend survey coverage in the Republic of Ireland. For areas not yet covered, the rates indicated for comparable areas may be used as an indication of likely corrosion rates.
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