Hot dip galvanizing FAQs

How thick is a galvanized coating?

The thickness of a galvanized coating is mostly determined by the thickness of the steel section being galvanized.  For example the British standard for hot dip galvanizing, BS EN ISO 1461 (2009), states that 6mm thick steel should have a minimum mean galvanized coating thickness of 85 microns and a steel section of 3mm – 6mm should have a minimum mean galvanized coating thickness of 70 microns. Click for more information on coating thickness.

How long will my galvanized coating last?

Probably a very long time is the short answer. The longevity of most galvanized coatings will be determined by how thick the coating is and how corrosive the local environment is.  The air pollution in the UK is very low with most area’s annual corrosion rates being around one or two microns or even less.  Some aggressive environments corrode zinc faster.  Click for more information on how long galvanizing lasts

What is the longest length you can galvanize?

Our Hereford plant has a 10 metre long bath and we can double dip lengths of up to around 15.5 metres or so.  Please contact us if you are unsure if an item will fit into our bath.

How much will my hot dip galvanizing cost?

Hot dip galvanizing prices are usually calculated by weight.   Your galvanizer will give a price per tonne before galvanizing.  Your steelwork is then galvanized and weighed and the rate applied to this galvanized weight.  Always be aware that the galvanized weight of your steelwork will be higher than before it was galvanized (as it is now wrapped in zinc).  The galvanizing rate you are charged will depend upon a number of factors.  Straight forward heavy structural sections usually command a lower galvanizing tonnage price rate than lighter and more complex fabrications.  Please contact us for a quotation.

Is there a British standard for galvanizing?

The British standard for hot dip galvanizing is BS EN ISO 1461 (2009) “Hot dip galvanized coatings on fabricated iron and steel articles”.

How do I protect my threads from galvanizing?

Good question.  Protecting areas of your steel from the galvanizing process is tricky.  High temperature resistant masking tape, grease or paint are all tried and tested.  If protecting threads is an issue we would always recommend that you contact us as every job is different and options can be discussed to find the one to suit your application.

Why is my galvanizing no longer shiny?

The shine on all galvanized steel will fade in time.  How long it lasts will primarily depend on the ‘bling’ elements that some galvanizers use to extend the shine factor and, of course, the British weather.  To help the shine last longer, some galvanizers add shiny metals (in addition to the zinc) such as aluminium to their galvanizing metallurgy.

Others, dip their freshly galvanized steel into a passivation (as we can do at our Shropshire plant).  Both of these methods will help for a while but the weather will inevitably take the shine off as the zinc reacts with the atmosphere. It should be noted that bright and shiny galvanizing does not afford any better protection to duller greyer galvanizing.

What is the lead time for my galvanizing?

The leadtime for galvanizing is usually up to a week.  Faster turnarounds can be available but this will depend upon the galvanizer’s workload and the job itself.  It is best to contact your galvanizer to discuss the turnaround if a deadline is to be met.

Is galvanizing available in any colour options?

No.  As written above, galvanizing can have different levels of shine depending upon who your galvanizer is but the colour must always be described as ‘zinc’.  Powder coating galvanized steelwork is an option and a service that we offer (see our powder coating section) otherwise with the correct preparation you can wet paint the galvanized steel yourself.

Can you collect my steelwork or do I bring it in?

Both our Shropshire and Hereford plants operate their own transport service.  Please contact the relevant plant for details.  Alternatively, you can do the legwork yourself.

How do I repair damaged galvanizing?

Hot dip galvanizing is where molten zinc metalurgically bonds with the steel creating a very tough and durable coating.  However, in some extreme circumstances during transport, handling or erection damage can occur.  If this happens, we recommend that you follow the correct procedure, using the correct materials.

Click here to read our guide on how to repair galvanizing

Can a fabrication with contacting surfaces be galvanized?

Yes, providing that the edges of the contacting surfaces are not totally sealed by welding.  If gaps in the weld are not left then you must drill ventilation holes through the contacting surfaces.  These holes need to be a minimum 10mm or the thickness of both contacting surfaces combined (whichever is the larger).  If neither is done, the air trapped between the surfaces heats and expands during the galvanizing process and can explode causing damage to your fabrication and can be very dangerous for our operatives.

Linear contacting surfaces.  For example, where an angle is seam welded down the length of the flange of a beam: a vent hole must be drilled every linear metre or part metre. So, if the contacting angle is 6.5 metres long then there should be seven vent holes drilled through it.

Non linear contacting surfaces.  For example, where a large bracket is welded to a beam: a vent hole must be drilled when the contacting surface area is greater than 200 x 200mm.

For unusual contacting surface shapes or if you are in any doubt, please contact us for our advice.  We can only galvanize steelwork we deem to be safe and so will consult with you if we have concerns over steelwork we receive.

Can I weld galvanized steel?

Welding galvanized steel is possible using the correct method and under the strict conditions  Please note however, that the inhalation of freshly formed zinc oxide fumes that will result can cause illness so the correct advice should always be taken before undertaking.

Powder coating FAQs

Have I a choice of colours?

Yes. You can choose from a wide variety of RAL and BS numbers and other colours too.

What gloss level do you recommend?

Most, but not all, colours are available in matt (approximately 30% gloss level), semi-gloss (approximately 60% gloss level) and gloss (approximately 80% gloss level).  Full gloss is not generally recommended for external applications and we always recommend matt for when powder coating over galvanized steel.  Please contact us to discuss your requirements.

Can you powder coat over galvanizing?

Absolutely.  Most of our powder coating is applied to galvanized steel.  After galvanizing your steel, we fettle it and then T-wash it to ensure you receive the coating quality you expect.  The powder coating should be carried out of steel we have freshly galvanized to avoid any issues.  We do not fettle galvanized steelwork that we have not galvanized.

If powder coating gets scratched during installation how do I repair it?

No paint system is invincible and despite its durability, powder coating can be damaged in some circumstances.  In these cases we recommend that you purchase a tin of matching aerosol ‘touch up’ paint which should be applied carefully to the area in question.  Please contact us for more details on how to remedy scratches or for prices and availability on our range of ‘touch up’ paint.

Can I dress my own galvanized steelwork before you powder coat it?

For jobs that require galvanizing and powder coating, we have a created a department whose sole function is to fettle that steelwork.  However, as fellow obsessive control freaks, we respect the right of every man or woman to fettle their own work.

Is the powder coating packaged?

Yes, we package all powder coated steelwork for safe transport back to you or site.

How is the price of powder coating measured?

Unlike galvanizing (which is usually priced by weight) powder coating prices tend to be calculated by size or surface area.  Estimate how large your fabrications are and how many you have and give us a call for a quotation.

Do you powder coat to British standards?

We powder coat onto hot dip galvanized steel in accordance to BS EN 13438:2005.