What is hot dipped galvanised?
This is surely the most cost-effective method and, when utilised in the right environment, can be aesthetically pleasing. Steel is lowered into a ‘bath’ of molten zinc, removed and left to cool.
What other types of galvanising methods are there?
It’s important to distinguish the difference between the processes that may be referred to as ‘galvanised’. The finish normally associated with fixings is BZP (bright zinc plated) which is a thin layer of zinc applied using electrical currents. It is very neat but does not hold up with surface protection with the hot dipped galvanised method and isn’t suitable for larger items. Another method less commonly used is ‘cold galvanised’. This is purely the application of a zinc rich paint. It’s a cheap method and should not be the only protections; see below where using it with a powder coated top coat is recommended.
Is it worth hot dipped galvanising with a powder coated top coat?
To me, it is an unnecessary expense. Very often the 2 processes are carried out by different companies at 2 different locations. Even if that is not the case the steel requires fettling (taking off the sharp pieces of zinc) which can be time consuming to achieve a high finish. The answer here, in most cases, is to use a powder coated zinc primer. Click here to find out more.
Is a zinc rich primer as good as galvanising?
For longevity, the simple answer is no. However it is much cheaper when apply a top coat later as the primer doesn't require fettling or degassing, is less likely to have a reaction with the top coat (we've seen bad cases of bubbling before) and both coats will be done at the same premises.
What is fettling?
Fettling is required to remove the sharp zinc pieces created in the hot dipped galvanising process. This is generally done using soft sanding pads attached to power drills or angle grinders and, for the more delicate jobs, hand files and sandpaper can be used.