In the 21st century, every country in the world now has many hundreds of thousands of tons of steelwork that is being protected by hot dip galvanising or paint coatings. These structures can be telecommunication towers, steel road and rail bridges, crash barriers along the highways, steel lighting poles, overhead road and rail gantries and many more steel structures.
Paints and hot dip galvanising (HDG) has done an excellent job of keeping all of these structures protected against corrosion for a very long time, and in fact one of the oldest HDG transmission pylons is in Los Angeles, California, and it is now 99 years old, which is an incredible service-life to have from a single layer of zinc.
HDG zinc has been in use for well over a hundred years now, and it is still very popular all over the world. Why is this system so popular?
With regards to the maintenance of these structures, hot dip galvanising (HDG) is far superior to any paint system as it will never peel, crack, blister, flake off or delaminate in layers. It simply depletes in thickness from the top of the zinc coating, and the depletion-rate is dependent on the geographical location of the structure.
For example, an electricity pylon situated in the mountains could lose as little as 0.1 µm per year, and galvanised steelwork inside a coastal oil refinery could lose up to 8.4 µm per year (based on figures from the International Corrosion Research Association).
As the depletion is always from the top of the zinc layer, the lower sections of this layer will always remain intact on the surface of the steel, providing both cathodic and barrier protection properties, and will carrying on doing so until the zinc has all gone, whereupon corrosion will begin to corrode.
While the coating still has some remaining thickness, the 15 mm ‘throw’ will still be in place, so that where any physical damage from a heavy impact or abrasion takes place, the ‘throw’ (or in scientific terms the ‘linear polarisation’) will still be able to protect any exposed steel surface within 15 mm of the zinc’s edge.
The big problems can arrive when the zinc layer is fully depleted on a structure like and overhead gantry or an electricity transmission pylon, where the dismantling of the structure for re-galvanising is never an option. It is not always possible to turn off the power to thousands of homes and businesses to replace pylon components, because it could several days. It is also very expensive to close down highways in order to dismantle overhead sign-gantries and other heavy steel structures without causing massive traffic disruptions and lane closures, which run into thousands per week in costs.
During the early 1970’s, this future problem had already been forecast by a chemist, and he produced a liquid zinc product that could actually re-galvanise these structures on site, or in-situ wherever they stood.
So the galvanising product ZINGA was born, and it was developed into a solution specifically for the repairs and the re-building of HDG. Why? Because this chemist realised, even back then, that at some point in the future there would never be enough time or money to dismantle so many millions of structures worldwide and replace them with new ones. So the concept of ‘on site galvanising’ was born.
Like hot dip galvanising, ZINGA has some excellent attributes.