Do's & Dont's
- Clean or remove all metal deposits after constructing the roof: Loose fasteners, pop-rivet mandrills, metal drillings/objects increase the risk of corrosion and should be removed.
- Prevent demage to paint coating: This damage could increase the risk of corrosion if considered to be severe. In the areas where the corrosion is evident(i.e. overlapping sheets and sheet ends), the corrosion will spread unless treated in good time. Clean the corroded edge thoroughly and repaint.
- Repainting of roofs: If the need should arise to repaint a Chromadek® roof, it can be done with an appropriate roof preparation method and a suitable paint system. Contact Arcelor Mittal South Africa for advice and referral to approved and reputable roofing finisher(s).
- Walking on roofs: Avoid abrasive contact, soft contact is recommended.
- Scheduled roof maintenance: It is recommended that roofs are cleaned and washed regularly.
- Roof location:Avoid adverse conditions.
- Roof pitch:The minimum roof pitch permitted as per SANS10237 is 2 degrees. Any roof pitch < 2 degrees is seen as a flat roof that could be more problematic in terms of corrosion because of static water.
- Correct type and class of fasteners must be used for a specific area and regional application.
Acceptability of direct contact between metals or alloys with metallic zinc coating for Chromadek®
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Cladding material
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Accessory or fastener material
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Aluminium and aluminium alloys
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Copper and copper alloys
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Stainless steel
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Zinc-coated steel and zinc
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Aluminium/zinc alloy-coated steel
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Lead
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Atmospheric classification
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C4+
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Other
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C4+
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Other
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C4+
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Other
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C4+
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Other
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C4+
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Other
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C4+
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Other
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Zinc-coated steel and zinc (Chromadek)
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Yes
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Yes
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No
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No
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No
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Yes
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Yes
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Yes
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Yes
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Yes
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No
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Yes
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C4+ = Corrosivity category C4(high), C5-1(very high - industrial) or C5-M (very high- marine) according to ISO9223.
Other = Corrosivity category C1(very low), C2(low) or C3(medium) according to ISO9223.
"Yes = Acceptable" and "no= not Acceptable" imply the following:
i) Yes = Acceptable, because of bimetallic contact, either no additional corrosion of the cladding system will take place or, at the worst, only very slight additional corrosion. It implies that the degree of corrosion would not significantly shorten the service life.
11)Not Acceptable - moderate to severe corrosion of the cladding or accessories will occur, a condition which may result in significant reduction in the service life.
- Cladding systems should be designed so that there's no direct contact between incompatible metals or alloys. Where the use of incompatible materials is unavoidable, they should be separated by using an imprevious non-conducting material
- It is preferred that fastening systems be designed so that direct contact between two or more incompatible metallic coatings or alloy cannot occur.
- Staining and damage Chromadek® surface A roofing system shall be designed to prevent drainage from one surface damaging or staining a lower surface, this aspect needs to be taken into account when solar panel installations are contemplated
- A roof should be designed to prevent drainage from one surface damaging or staining a lower surface
Acceptability of drainage from one surface to a lower metal of alloy surface
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Roofing and cladding material
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Lower cladding/accessory material
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Aluminium and aluminium alloys
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Copper and copper alloys
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Stainless steel (300 series)
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Zinc-coated steel and zinc
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Aluminium/zinc alloy-coated steel
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Lead
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Zinc-coated steel and zinc (Chromadek)
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Yes
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No
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No
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Yes
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Yes
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No
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Whilst drainage between the materials shown would be Acceptable, direct material contact should be avoided. (Also see the correct class of fasteners).
"Yes" implies dissimilar metal drainage from top surface to lower surface "Acceptable" and "No" implies "Not Acceptable". "Acceptable" and "not Acceptable" imply similar service performances to those noted in the correct class fastener
- Special fixtures for fitting solar panels: Galvanised fixtures recommended, however, see correct class of fastener and different metal compatibility for guidelines.
- Cutting of Chromadek® roof sheets: Avoid swarf and sparks from angle grinders. (Angle grinders must not be used). Suggested alternatives: circular saw and nibbler cutting.
- Storage of material: Do not store material (roof sheets and or coils) outside in the rain or in wet conditions. Always ensure that the material is stored under cover in and enclosed storage area. Ensure adequate ventilation during storage.
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