Using Bluescope REDCOR® for Fielders Finesse® Cladding

Subject to minimum order quantities and extended lead times Fielders is able to offer REDCOR® weathering steel across the Fielders Finesse® range of architectural roofing and walling profiles.

Characterised by its weathered appearance and burnt orange colour, REDCOR® has become a popular selection for architects and specifiers, alike. This distinct material does require special consideration when applied, particularly in façade applications. The information stated herein should be read in conjunction with Finesse® range Design Data pages and installation details for Non-Cyclonic and Cyclonic applications, as applicable.

What is REDCOR® weathering steel?

REDCOR® weathering steel by BlueScope is a high strength, low alloy structural steel with enhanced atmospheric corrosion resistance compared to conventional structural steels in certain environments. REDCOR® steel forms a tightly adherent oxide layer, known as the “patina”, that confers the enhanced corrosion resistance.

REDCOR® weathering steel grade used for the Fielders Finesse® range is a high phosphorus steel complying with AS/NZS 1595 and is consistent with grade CW300-G with a thickness of 0.7mm.

Published Finesse cladding range capacities and span data for 0.75mm BMT may be applied to 0.7mm BMT Finesse cladding products manufactured using REDCOR® weathering steel.

Detailed information regarding BlueScope REDCOR® weathering steel is available in BlueScope Technical Bulletin 26.  This information provided here provides a summary of this in relation to its use with the Finesse range.

Formation of the "Patina"

REDCOR® weathering steel develops a stable oxide layer, known as the “patina”, that is tightly adherent to the base steel and consequently helps to resist continued corrosion over extended time frames. The stable oxide layer of weathering steels is a result of three factors:

• The alloy composition of these types of steels
• Exposure to wet and dry cycles
• A suitable atmospheric environment

REDCOR® weathering steel develops the protective patina layer when exposed to alternating periods of wet and dry and hence requires bold exposure for the patina to develop. The colour of the patina changes over time. When first formed the patina will be bright orange, but over time it will change to a dark brown, almost purple colour. The rate of development of the patina depends on the degree of exposure to the weather and the presence of contaminants such as chlorides and sulphides in the atmosphere.

In situations where one surface of a structure incorporating REDCOR® weathering steel receives more exposure than another there is likely to be a difference in appearance between the two surfaces. The more boldly exposed surface will form the patina more rapidly, whereas the protected surface will form the patina more slowly and have a rougher surface texture than the exposed side.

Limitations of REDCOR® weathering steel

It is important to note that REDCOR® weathering steel is not suitable for all applications and in all environments.

Specifically, REDCOR® is not recommended in

• Marine environments with high salt deposition rates.
• • The proximity to the sea for which REDCOR® weathering steels can be used depends on a variety of factors – wind direction and strength, presence of breaking surf and topography. In general weathering steel should not be used within 2 km of the coast
  • Similarly, micro climates should be considered. Eg splash zones around swimming pools, proximity to irrigated landscape areas etc
• BlueScope REDCOR® weathering steel is not recommended for heavy industrial locations where high concentrations of sulphides likely to be present in the atmosphere, for example adjacent to smelters in locations such as Port Pirie or Mt Isa.
• REDCOR® weathering steel is not recommended for applications where the structure is constantly wet, such as submerged in water, being buried in soil or in areas of very high rainfall and humidity.
• REDCOR® weathering steel should not be used where the relative humidity exceeds 80% for more than 60% of the time.
• Where REDCOR® weathering steel is used to span water a minimum distance of 2.5m is required above the water surface.

Design considerations

Correct detailing is essential when using REDCOR® weathering steel to ensure there are no inter-material issues with the structure and that staining of the surrounding areas does not occur.

In all detailing work it is important that the structure has good ventilation to enable the proper development of the patina, additionally some important principles that need to be considered are:

• Eliminate entrapment points where moisture or debris accumulates. For Fielders cladding range, a vertical orientation is recommended for all wall cladding applications using REDCOR® weathering steel.
• Avoid expansion joints wherever possible. Where joints are unavoidable seal the joint using an appropriate material such as EPDM or silicone.
• Water running over the surface of REDCOR® weathering steel during development of the patina has the potential to stain downstream surfaces. Run-off should be considered at design stage and controlled to prevent run-off to surrounding structures. The following methods should be considered:
• Diversion of run off by drip plates, sloping surfaces, downpipes and drains to carry the run off away from the structure.
• Use of coverings or coatings on sub-structure.
• Correct use of landscaping to collect the run off.
• Careful consideration should be given to the location where REDCOR® weathering steel is to be used:
  • Pedestrian traffic proximity should be considered as;
    • Contact with clothing may result in staining to clothing.
    • Oils from hand marks etc will affect the uniformity of the patina
  • Microclimatic considerations should be assessed
    • Splash zones around swimming pools
    • Irrigated landscape areas
    • Outdoor cooking areas etc

Handling and preparation of Fielders Finesse® using REDCOR® weathering steel

Fielders Finesse® cladding made using REDCOR® weathering steel is supplied with CORSTRIP® to protect the surface during installation. However, care should be exercised in the handling of REDCOR® weathering steel. The surface must be kept free from oil, chalk marks, paint, gouges, concrete splatter and similar staining by other construction materials. Any foreign matter adhering to the steel surface needs to be removed as soon as practicable.

Hand-marking of REDCOR® steel

REDCOR® steel can be particularly susceptible to hand-marking both during and after installation. During installation the supplied CORESTRIP® coating will provide adequate protection from hand marking. Where this coating needs

to be removed during installation gloves should be worn when handling the product. Where the product is installed in locations susceptible to handling or touching after installation, it should be acknowledge that hand-marking may occur and be visible for an extended period of time.

Fixing facades

The fastening of weathering steel facades should follow the general principles outlined above. Weathering steel panel must be fastened in such a manner as to allow for adequate wet and dry cycles. Crevices must be avoided to ensure that the structure does not corrode and the run off must be controlled to prevent staining of the façade and surrounding structure.

Compatibility with other materials

As with all metals, care must be exercised in terms of connecting dissimilar metals to REDCOR® weathering steel. When joining stainless steel to weathering steel a spacer or gasket should be used. REDCOR® weathering steel should be isolated from ZINCALUME® steel or zinc-coated steel support sub-structures by use of a heavy-duty (min 250 micron thickness) self-adhesive tape such as TREMCO ALTA 300-40 Isolation tape or equivalent. Tape should fully cover and extend 50mm beyond support members.

Fixings

Fixing is achieved using 304/316 grade stainless steel screws, provided an isolating gasket is used to keep the two different steel types isolated. Eg EPDM washers.

 

REDCOR® Technical Bulletin