There’s a mind-boggling array of finishes for steel fixings.
In a nutshell:
- There is a wide range of finishes for steel fixings in architectural façade and solar shading projects
- Hot dip galvanising (HDG), bright zinc plating (BZP) and uncoated stainless steel are the most common
- BZP won’t prevent rusting or oxidising if used outside
- HDG provides a weather-resistant layer that protects steel from corrosion
- A2 and A4 stainless steel is strong and resistant to surface corrosion
- The choice will come down to budget, location, expected lifespan and aesthetics
Most people have heard of galvanising and zinc-plating... but what about chemical blacking, green chromate or sherardising? And when is it best to stick with uncoated stainless steel?
- Bright zinc plating (BZP) is a common finish for many fixings, and is applied to standard steel or alloys during manufacture. It’s a low-cost option but the layer of zinc is thin, so it won’t prevent rusting or oxidising if used outside.
- Hot dip galvanising (HDG) (as the name suggests) is a process where fixings are dipped in a bath of molten zinc. It’s thicker than BZP, so provides a weather-resistant layer that protects steel from corrosion. It’s not as bright and shiny as BZP, but can be used outdoors – say, for brise soleil or façade projects.
- Stainless steel is strong and resistant to surface corrosion. There are two main grades, A2 and A4, and both are resistant to rust – although A2 can tarnish over time. A4 is best for marine environments. Initially, both will have a polished finish – but that may not be what you want.
What finish is best?
There are pros and cons for each of the most common coatings, or stainless steel grades. Ultimately, the choice will come down to budget, location, expected lifespan and aesthetics.
The dull look of HDG (or the shine of stainless steel) may detract from the overall aesthetic. It’s possible to shot-blast the heads of fixings to create a key that can be powder-coated, and there’s a chemical process to dull or blacken stainless steel.
Alternatively, have you thought about placing the fixings where they can’t be seen?
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