The dictionary definition of galvanise is “to coat (iron or steel) with zinc”. Hot dipped galvanising is a well-established process used to protect steel from corrosion by applying a layer of zinc. Steelwork is immersed briefly in molten zinc with layers. There is however, another process that can be used to galvanise steel.

Thermal & Arc Sprayed Zinc Galvanising –

The Alternative to Hot Dip Galvanising

Metal spraying using Flame or Arc spray is an alternative method of zinc application. Both systems involve the projection of small molten particles of zinc onto a prepared surface, where they instantly cool and adhere to form a galvanic coating. The thickness applied is dependant on required performance level.

Gardwell have been successfully applying the Metallisation flame spray system for many years, part of the recent investment has included the acquisition of the latest Arc Spray application equipment. This cutting edge equipment enables faster more efficient application with improved adhesion and a lower impact on the environment.

As a protective system for steelwork it is unsurpassed, being the only system recommended by International and European Standards EN ISO 14713, as giving greater than 20 years life to first maintenance in very aggressive environments such as coastal, splash zone and salt water immersion.

Thermal spraying has proved itself to be extremely effective in its 90 years existence, in all manner of applications as a practical, efficient and higher performing alternative to hot dip galvanising. The offshore oil and gas industry, network rail, highways, sub-sea, petrochemical and countless other industries have been prolific users and supporters of this system.

WEIGHING UP THE TRUE COSTS

The galvanising process will always have a place in industry, but there can be some disadvantages which makes thermal and arc spray the preferred and practical choice.

Distortion

The dipping process for galvanising involves prolonged exposure to high temperatures; this can result in fabrications becoming distorted or twisted.

Thermal and Arc spray does not cause any kind of distortion.

Fettling

It is common for galvanised items to require fettling, a process which involves grinding down areas of excessive thickness, drips, inclusions and the occasional sharp edge before painting.

Thermal and Arc sprayed surfaces require no fettling; the surface finish is clean, uniform and ready to paint immediately after application. This reduces cost and time in preparation for painting and ensures a clean finish is quickly achieved. There is also no requirement to etch surfaces before coating.

Adhesion

Thermal and Arc sprayed coatings have the finished porous texture of fine sandpaper. When over coated, the paint is absorbed into the surface and further grips to the fine textured surface. This results in superb mechanical adhesion values.

Surcharges

Galvanisers generally apply a surcharge for their work.

Gardwell does not apply any additional charge for the application of zinc.

Hollow Sections

Capped hollow sections normally need to be drilled for the galvanising process, this is to avoid the risk of the air inside expanding and causing the section to split.

Thermal and Arc spray zinc application does not create such high heat levels, therefore there is no need to drill holes to release pressure.

Size & Weight Restrictions

Galvanisers are limited by the size of their dip tanks and the capacity of lifting equipment.

Gardwell however is not governed by these limitations and is able to apply zinc using thermal or arc spray equipment to almost any size or weight of structure.

Pre-treatment

For the galvanising process items which have existing coatings need to be stripped or blast cleaned before they can enter the dipping process, many galvanisers will not accept work until this pre-cleaning has been carried out.

Gardwell however carries out all of the preparation in house, all surfaces which are to be zinc coated are blast cleaned. Blasting cleaning is carried out to ISO 8501-1:1988 standard, this means that all traces of existing coatings, rust and scale are removed leaving the optimum surface for longevity and performance of the zinc.

We invite all potential users of Hot Dip Galvanising to speak to us before placing their orders, we are confident that we will be able to offer a cost effective and efficient high quality alternative. In most cases our galvanising system has proven to the best cost and long term solution for our clients galvanising needs.