The act of galvanising steel is designed to create a protective zinc layer to the external face of the steel material. This protective layer then protects the internal steel structure from rust or corrosion. The galvanisation process is applied to the entire steel section/sheet which is then cut down to order.
When galvanised steel is cut, welded and cleaned this protective zinc layer on the outside of the steel is slightly compromised at those areas.
Although powder coating gives an element of protection to these joints and edges there is a small chance that oxidisation could occur on the corner joints or cut edges of a galvanised steel profile.
If steel systems are installed within a ‘harsh environment’ then the chance of oxidisation and premature ageing increases. A ‘harsh environment’ is any area where higher than average chemicals, salts or compounds are in the air.
This includes, but is not limited to;
- Swimming pool environments
- Projects near a natural water source
- Projects within 5 km of the coast or sea
If your steel window/door is to be installed in a ‘harsh environment’ you may want to consider specifying a stainless steel frame. Stainless steel has a much higher density and a lower chance of corrosion than mild or galvanised steel so is better suited to these environments.
Please be aware that stainless steel is a more expensive material and will increase the cost of your glazing installation.
It is important to note that you are still using a steel product and although (through galvanisation and powder coating) every effort is made to protect the steel it will, over time, experience some element of aging or corrosion.
NOTE Powder Coated Finishes for Steel
Galvanised, Mild and Stainless Steel can all be powder coated to finish the metal in the RAL colour of your choice.
Dry Powder Coating is the most common method. This involves the even application of charged polyester particles to the frame which is then baked to create a coloured seal to the metal frame. Dry Powder Coating may not be suitable for architectural metal works with intricate detailing as the polyester particles will slightly fill in any delicate notches, lines or detailing.
For these more decorative elements of metalwork, Wet Powder Coating is better suited. This coloured finish is applied by hand using a wet spray. The process of hand applying the spray may result in slightly different colour thicknesses across the surface of the metal.
NOTE Care of Powder Coated Surfaces
If you chip or scratch a powder coated surface you will expose the base material of the metal and create a weak spot in the metal’s defences against corrosion. This point is then an area where moisture can penetrate the metal substrate and cause corrosion and oxidisation.
Care must be taken in the handling of metal elements to ensure that no damage is inflicted to the powder coated surface. This applies to the installation process, post-installation construction (where other works will be carried out on site) and once the project is completed.
Information regarding the protection and handling of metal profiles and products should be shared with all that may have interaction with the specialist architectural metal installation. This includes other trades, contractors, cleaners and the end user.
Chemically Blackened Steel
The chemical blackening of steel is a specialist architectural metal finish used to create a dark, matt appearance to steel profiles. It is achieved by hand applying the blackening chemical to the surface of the steel.
Due to the artisan nature of the finish, the colour achieved may not be completely uniform across the steel surface. The chemical agent will also react to any differing material thicknesses or compositions in the surface of the steel alloy which could also cause differing colours across the surface.
NOTE Chemically Blackening Galvanised Steel
We do not recommend applying the chemical blackening compound to galvanised steel. The reaction between the zinc in the galvanised steel and blackening chemicals results in an extremely uneven finish.
For this reason, we only apply chemical blackening to Mild Steel. Therefore chemically blackened steel is only suitable for internal environments in non-swimming pool locations.
The process of patinating bronze speeds up the natural ageing process of architectural bronze through the application of chemicals to the surface. The length of time the chemicals are left on the bronze determines the ‘colouration’ of the patina (light, medium or dark BMA).
Once the preferred bronze finish has been achieved another chemical is applied to the architectural bronze to stop the accelerated ageing process. This does not stop the bronze from continued ageing over time. It is important to note that Patinated Bronze is an organic finish and likely to change, darken and colour over time. This then further accentuates the antique finish to the bronze frames.
The positioning of the metal, exposure to sun and rain and manual handling of the frames will all help contribute to the changing appearance of the bronze overtime.
NOTE Steel Lacquering for External Use
Lacquering of steel or architectural metal can be used in some instances to seal the architectural finish to the metal and reduce the speed of further ageing. However, lacquering is only recommended for internal applications in non-harsh environments.
If lacquered steel is installed externally or in harsh environments you may see ‘blistering’ or other defects in the lacquered surface exposed to the elements.
Corten (or weathered) steel was originally designed for large industrial projects such as bridges. The material was designed to naturally oxidise on the surface over time. This oxidised layer on the outside of the steel then creates a protective coating to the metal underneath.
In order to create architectural metal works with a weathered finish upon installation, we can accelerate this ageing process using chemicals. The metal will then be installed on site with a pre-weathered appearance.
To protect other building finishes from the ‘flaking’ and staining inherent with the use of Corten Steel we seal the rusted surface with wax. The purpose of the wax application is to reduce the amount of staining to the surrounding building finishes, such as flooring and adjacent building finishes.
In order to maintain this protective layer, the wax must be reapplied regularly. The regularity of reapplication depends on the environmental factors of the installation.
NOTE Building Staining from Corten Steel
Due to the engineered properties of Corten (weathered) Steel, the surface is changeable. When Corten is exposed to the elements, such as wind and rain, small particles of the rusted surface will flake off and settle on the surrounding surfaces. This is called staining.
When selecting Corten Steel for your project you should carefully consider the materials used in close proximity to the steel installation. Light coloured surfaces or porous materials are more likely to show this staining.
Cleaning of Architectural Metal
- Do not use harsh abrasives or chemicals
- Do not use scrubbing brushes or sponges with bristles or rough surfaces
- Do not use acidic cleaning products
- Clearwater with a neutral pH is recommended
- Soft wiping with a non-abrasive cloth is recommended
- Frames and glass must be fully dried after cleaning
- When the glass is cleaned it is important to ensure that all water is dried from the glass surface, in particular, any crevices or corners of the glass where it meets the frame. If this is not done the water may cause corrosion to the profiles.
- All parties involved with the maintenance and cleaning of the installations must be given a copy of the O+M manual to ensure proper handling. This includes all external cleaning services, property maintenance and building users.
Questions to consider when selecting what architectural metal finish is most suited:
- Is it a residential or commercial installation?
- What is the access to the installation point like?
- What type of environments are the frames going to be exposed to?