Galvacoat & Galvanizing from Wedge Group Galvanizing Ltd
By offering the perfect combination of sustainability, ease of application and long-lasting protection, it's no surprise galvanizing is the finish of choice for industries as diverse as manufacturing, engineering, and construction.
It is used in a variety of projects, ranging from Olympic-related infrastructure right through to multi-million pound railway station upgrades, and major construction initiatives. But, it is a process that has previously thrown up a number of practical issues when the steel needs to be painted to provide an aesthetically-pleasing end result.
In this article, Trevor Beech of Wedge Group Galvanizing, explains how the galvanizing process works and the technology behind it, the common problems associated with products traditionally used to coat galvanized steel, and how a new specially developed paint will put these problems firmly in the past.
"For the vast majority of steel-related projects, hot-dip galvanizing is simply the most effective method to provide a long-lasting protective coating against rust and corrosion. Because it forms a series of alloy layers with the steel, it is much more robust than other coatings that only bond chemically or mechanically, and also has the added advantage of fully coating the steel, both inside and out.
To prepare the steel for the galvanizing process it must be cleaned, which involves the complete removal of light grease, scale and dirt using a variety of techniques. Commonly, the steel is dipped into an alkaline or acidic degreaser and then rinsed before being dipped in a hydrochloric acid rinse at room temperature. The product is then rinsed and dipped in a flux solution which removes the last traces of oxide from the surface and coats the product with a thin film of flux.
The process involves steel being dipped into molten zinc at temperatures up to 450oC, where a series of zinc-iron layers are formed by a metallurgical reaction between the iron and zinc creating the protective coating. The main thickness of the coating is created at this time, so even if the steel remains in the galvanizing bath for a considerable time, it will not form an overly thick protective layer. Typically, items will be dipped for an average of four or five minutes, and when removed a layer of pure molten zinc will be taken out on top of the alloy. It is this that cools and results in the bright, shiny appearance generally associated with newly-galvanized products.
Once steelwork has been galvanized, there are occasions when colour needs to be added to either complement a company's existing branding, or perhaps to create a greater visual impact - whether it's steel balconies or gates at housing developments, gantries at supermarket fuel stations, or even structural metalwork for major building projects.
The biggest challenge in adding colour to galvanized steel is achieving proper adhesion, and most problems start with pre-treatments, poor surface preparation, or the wrong choice of coating system. Standard paints aren't designed for use on ferrous metals which often means that when used, the paint doesn't bond adequately to the galvanized surface, and consequently peels or flakes prematurely - an end result that leaves an aesthetically poor finish, not to mention the time and effort required to repaint the steel.
Various coating types have been developed over the years to tackle this issue, to varying degrees of success. However, there is a solution; Galvacoat®, is a one-coat, two component polyurethane-based paint which has been specifically designed for use on galvanized steel and so eliminates the requirement for any special etch primers, while it gives GT0 adhesion for the entire duration of its coating.
GT0 adhesion is the British Standards test method for adhesion classified GT0 (BS 3900 Part 6 on galvanized steel). The test involves a painted steel surface being cross-cut to leave small squares, which when sticky tape is applied all over, will rip the paint from the steel if the bond isn't strong enough - GT0 classification is only achieved in instances where the tape cannot remove any paint from the steel, providing its adhesive qualities. It also has excellent resistance to UV exposure, and is suitable to be applied as a topcoat in outside weathering conditions.
The paint is available in all RAL and BS colours at different levels of gloss, allowing the end contractor a huge degree of design freedom, but just as importantly, galvanizing provides an ideal primer for it. Galvacoat® is applied by brush, or by air or airless spray, to a surface that is free of dust, rust, oil, grease and soluble salts, while for zinc surfaces, a combination of degreasing or steam cleaning is advised to ensure maximum effectiveness.
For use in areas of low industrial output, a dry film thickness of 80 microns can last for a minimum of 8-10 years, while a thicker coating can lead to similar results even when used in particularly heavy industries or coastal areas where high amounts of chemicals or salts can attack the coating. This drastically reduces, or eliminates completely, the need for repeated on-site maintenance and replacement costs.
Despite only being available here in the UK for a relatively short period time, the paint is already proving hugely popular. It has received significant interest from a diverse range of industries and projects, from being applied to bring steel staircases and external railing to life, to adding a touch of colour to signage and structural steel columns. Galvacoat® has recently been supplied for a bridge project in Jersey
We supplied a significant order to leading retailer Tesco, who used it to protect steel gantries installed on the forecourts at all of its petrol stations across the UK. The project saw more than 600 individual steel frames galvanized, and then coated using the paint system. Due to some being installed at coastal locations where they will be exposed to the elements and severe weather conditions, Galvacoat® was the perfect finishing solution.
Wedge Group Galvanizing is the sole distributor in the UK for Galvacoat®, for more information visit the website or email: firstname.lastname@example.org.
For further information please email Wedge Group Galvanizing Ltd