FAQs

Dark grey or light grey – it’s all galvanized.

Protection is equal – and often better – with dark grey coatings than with light grey coatings.

Variation in colour is generally due to variations in the chemical make up of the steel being galvanised. Due to these variations steels can be much more reactive with zinc resulting in very different appearances E.G. Silicon content of steel is particularly important. A dull, dark grey finish is usually a much tougher and more corrosion resistant coating than a shiny finish. Each of these finishes are entirely acceptable according the British standard EN 1461. resistance as zinc, thickness for thickness can have better intrinsic corrosion resistance in acid industrial environments. These thick coatings can be more susceptible to mechanical damage particularly if handled roughly, and appropriate care must be taken.

The dark grey coating surface may develop iron oxide staining on atmosphere exposure, even in mild conditions when moist. This is only a surface effect and does not develop into nodular or flaking rust: the galvanized coating remains intact to protect the steel.

For the most current up to date information regarding venting and draining holes please see: https://www.galvanizing.org.uk/design-for-galvanizing/filling-venting-and-drainage/

The galvanizers association has advised that a standard galvanized coating may now achieve a coating life of 50 years in most environments, although urban / marine are up to 25 years.

For further information see https://www.galvanizing.org.uk/corrosion-map/

Maximum Material Dimension

*Max weight lift – 5 Tonne*
*Double dip 12m long as a straight length*

Contact sales team for any technical queries.

Discolouration and staining have no effect on the life of the coating. However, affected areas may be cleaned to improve the appearance of the structure. Generally, wire brushing or the use of a scouring powder will remove the stain and leave a sound galvanized coating.

For those fast – jobs that just can’t wait, the ‘NK Express Service’ offers a 24 hour turn around and is available on request.

Sound galvanized steel with many years of corrosion-free life ahead can sometimes be rust stained or discoloured. This may give an incorrect impression that the coating has failed and is, in some cases, visually unacceptable. Below illustrates the main causes of staining and discolouration and indicates how the problems can be avoided or the effects remedied. The staining and discolouration of galvanized coatings by rust may occur as a result of one or more factors:

1. Direct contact of galvanized parts with unprotected or inadequately steel (e.g. galvanized steel sections fastened with unprotected, electroplated or painted steel bolts).

2. Deposits of iron dust and swarf from other operations or sources onto the galvanized surface.

3. Water draining from unprotected or poorly protected steelwork, e.g. from damaged areas on painted steelwork.

4. During pickling, hydrochloric acid may penetrate into the weld area via pin holes or if the welding is intermittent. Residual salts can sometimes pick up water and cause ‘weeping’ from the weld areas. This effect is normally limited to a small area, ceases after a short time and is not detrimental to the coating.

5. Rusting of areas welded after galvanizing and subsequently left unprotected or inadequately protected.

6. Staining of galvanizing can occur when water runs off other materials notably metals such as copper, certain hardwoods, e.g. oak, an indeed whenever water can dissolve materials from one surface and redeposit on the galvanized steel.

Galvanizing lead times vary depending on the volume, size and type of material. Generally the process of galvanizing takes approximately half a day, though consideration must be taken on the time of year and how much demand there is within the industry. Contact us at the early stage in the planning process so that we can advise you on suitable methods of design and fabrication. Many delays are caused by inappropriate design and a lack of understanding of the galvanize process.

Small areas of galvanizing may be damaged by operations such as cutting or welding after galvanizing. Because of the sacrificial action of zinc, small localised flaws (typically up to 5mm diameter) tend to be self-healing and have little effect on the life of the coating. Nevertheless, it is often aesthetically desirable to renew the coating over small areas as well as larger areas using one of the following techniques:

a) Thoroughly wire brush the affected areas and apply several coats of zinc rich paint to give a coating thickness at least equivalent to the original galvanizing.

b) Thoroughly wire brush, heat the bare area with a blow torch to 300C and apply a special zinc alloy rod.

Painting with zinc rich paint is usually simplest but if a colour match is important, the zinc alloy rods are usually most suitable.

Contact the sales team for technical queries.

All parts of the structure should receive comparable corrosion protection where possible. The thinner zinc coatings frequently supplied on steel mesh, sheet, wire and tube will not last as long as those of products hot dip galvanized to BE/IS EN 1SO 1461, the standard which covers all structures galvanized after fabrication.

Welds should be continuous and slag-free wherever possible to minimise the retention of pickle residues.

Design structures to avoid run -off water from other metals on to galvanized steel. In particular avoid run-off from inadequately protected steel and from copper.

Where welding after galvanizing is necessary, welded areas should be thoroughly cleaned and the zinc coating restored either with an appropriate thickness of zinc rich paint or with a proprietary repair compound, in accordance with section 6.3 of BS/IS EN ISO 1461.