Technical Articles
Which galvanising finish is best?
Published 17 December 2018

Shiny or dull grey, differences in appearance are common, but can we choose the finish we want? Both photographs are taken not more than 24 hours after the galvanising process. By looking closely at the dull grey finish to ascertain why it looks the way it does, we can find the answer. During the steel production process silicone is added to some steels to a greater or lesser degree, this is what causes the dull grey effect. The second photograph clearly shows that two different steels have been welded together, to form a lintel. The square hollow section is almost all grey and the flat bar welded to it is shiny. Obviously both pieces have been through exactly the same process to get them galvanised, at exactly the same time. And, they have been through the same process on the same day as the “shiny” steel shown in the first picture. Therefore to answer the question: Can we choose the appearance of the finish? The simple answer is, no we cannot. We must therefore look at the difference between the two finishes, they are both fully galvanised, and they both offer the same level of corrosion protection. The dull grey finish, which has formed a zinc iron alloy on the surface, is quite often thicker than on shiny galvanised coatings, harder and more abrasion resistant. So irrespective of aesthetics it could be argued that the dull grey finish is better. It should also be noted that when exposed to atmospheric conditions all galvanised steel will weather to a dull grey colour.

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