Galvanising Made Simple

In coastal climates, a completely intact coating that has been applied too thin (for example, at the edges not rounded correctly) may allow chloride ions on the surface to penetrate the paint film to the steel surface underneath.

It is therefore very important that the paint specifications are followed to the letter, otherwise errors may occur. It usually costs four to five times more to correct the errors than the original cost was, because of all the extra work afterwards.

Hot dip galvanizing (HDG) has been the accepted way to protect steel for many decades. HDG eliminates many problems that may occur with surface treatment in the form of paint application.

Having said this, it is understood that also hot dip galvanizing has its own parameters that must be followed to achieve a good result. Tubular closed details must for example be provided with a vent hole per meter with 25 mm diameter, to prevent explosion when heated.

Architects & Engineers don’t particularly like to have holes drilled in carefully designed structures, and filling them later is a laborious and expensive process.

Another concern is the risk of warping of thin steel parts due to the high heat of the HDG process. Even a very small deviation means, for example for a long I-beam that the bolt holes no longer match the holes on the second beams. It also happens that some steel alloys have a different surface structure than ordinary steel and this can be a problem for hot dip galvanizing. Thus it can be difficult to achieve a uniform design of a welded construction composed of several different steel types. Some metals, such as cast iron are difficult to hot dip, and cannot be dipped in a liquid zinc bath with temperature at 450 degrees, because this would lead to bursts.

During the early 1970’s, a system for film galvanizing called ZINGA was developed in Belgium. ZINGA, apart from being a recognised galvanising system in its own right, is also used as a touch up for existing structures that cannot be removed and were previously treated by hot dip, such as high-voltage electricity pylons, bridges and traffic sign posts.

Film galvanizing with ZINGA offers the same type of cathodic protection as hot dip, but it is applied in the same manner as a paint system. The liquid galvanization consists of atomized zinc particles, resins and binders.

The method quickly proved to work well for repairs and could restore or increase the zinc coating thickness. The excellent results with these kinds of repairs convinced more and more engineers, manufacturers& fabricators to also use this method, among other things, in order to eliminate the problems with warping or distortion of thin steel parts. Even iron can now be galvanized, even if the application takes place at ambient temperature.

FILM GALVANISING combines cathodic / galvanic and barrier protection.
ZINGA can be applied by spray, brush or roller. Zinc content in the dry layer is at least 96%. It can be applied in a humidity up to 95% (avoid water droplets on the ground) and in temperatures down to minus 15 degrees Celsius.

“Example of very large section of steel, too big for HDG, Zinganised on site”

The zinc coating dries in ten to fifteen minutes and a second layer can be applied after an hour. Due to these properties, film galvanizing is greatly used in the offshore sector and in applications on foundations of ports and bridges. Ideal also for galvanising steel in tidal zones where limited time is available to coat the steel.

ZINGA can be painted for aesthetic reasons if desired, but it does not require any extra finish coating. A nice example of the long life performance of the surface is the Kalvoya bridge, outside Oslo. (See World-Wide References – Bridges) It was treated with ZINGA nearly 30 years ago and it is only now that a further refurbishment is being considered. Moreover, it has been found that a blasting will not be required before applying a new zinc coating, it will be sufficient to clean the surface to be treated under high pressure (700 bar). Tensile tests have demonstrated that the now almost 30 year old ZINGA layer still has an adhesion of 11 MPa.

This experience clearly demonstrates that it is possible to keep virtually all types of steel and iron constructions maintenance-free for a large number of years, giving them a full cathodic protection, provided they are properly cleaned and sandblasted, namely: with ZINGA film galvanizing system.

Check out the huge array of projects protected with ZINGA World-Wide – See World-Wide References Tab…

Testimonials