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COMPANY SPOTLIGHT GALVANIZING The past year has seen


the process of galvanizing continue to be the


finish of choice for the construction industry,in no small part due to its winning combination of long-lasting protection and sustainability


As one of the largest hot dip galvanizing organisations in


the UK,Wedge Group Galvanizing continues


to play aleading role in this trend, and in the


past 12 months alone has worked on an


incredibly wide range of projects, from Olympic- related infrastructure


and football and rugby stadium redevelop-


ments, to multi-million pound railway station upgrades and major construction initiatives


Wedge Group


Galvanizing’s Sales Director Trevor


Beech outlines some


of the science behind the process, before highlighting its


sustainable credentials ‘Jubilation’ by Lucy Unwin


What Does Galvanizing Involve?


The process is divided into two core areas: cleaning and galvanizing.Initially,the steel is chemically washed so that it’s in the perfect condition to react with molten zinc. The second stage sees the prepared metalwork submerged into abath of zinc to form the protective coating.


Cleaning the steel involves the complete removal of all grease, scale and dirt. Commonly,the steel is dipped into an alkaline or acidic degreaser,rinsed thoroughly in cold water,and then dipped again in hydrochloric acid solution. Particularly tough welding slag,paint and heavy greases may not be removed in this way so should be cleaned off before being


4 SURFACEWORLD january 2013 What is Galvanizing?


Hot dip galvanizing is the process of coating clean steel with alayer of molten zinc to form along-lasting,durable coating that will provide ongoing protection against rust and corrosion. The tough alloy layers formed during the process means that galvanizing is far more robust than other coatings that bond chemically or mechanically,while it also offers the added advantage of fully coating the steel, inside and out.


PROTECTION THAT CAN BE COUNTED ON


sent to the galvanizer.After the acid stage, the steel is rinsed and usually dipped in aflux solution, which is normally made up from Zinc Ammonium Chloride held in a temperature range between 65˚C and 80˚C. This final stage removes all final traces of oxide from the surface and coats the product with a thin film of flux.


Once the steel in dry,itisdipped in molten zinc heated to around 450˚C, at which temperature the galvanizing reactions take place. Finally,the work may be immersed in water to cool, or allowed to cool in air.


How Does Galvanizing Provide Such Strong Protection?


Once the steel is dipped into the molten zinc, aseries of zinc-iron alloy layers are formed very quickly.The main thickness of the protective coating is created at this time, after which the metallurgical reaction slows down. That means an overly thick protective layer won’t be formed, even if the steel remains in the galvanizing bath for aconsiderable time. Typically items will be dipped


for four to five minutes, and when they are removed alayer of pure molten zinc will be taken out on top of the alloy.It’sthis that cools to show the bright, shiny appearance generally associated with galvanized steelwork.


'Mare' asteel horse galvanized by Humber Galvanizing (continued on page 6)


read online @www.surfaceworld.com


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