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  1. #16
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    Quote Originally Posted by Bushmiller View Post
    I think much of the confusion around compatibility of galvanised iron and zincalume is to do with galvanic action and noble metals. In particular this issue is more acute when water is involved (guttering is the obvious sticking point). However, condensation forms beneath a steel roof so it can't be ignored. The foil backed building paper is probably sufficient insulation to separate the metals, but others are better qualified to advise on this.

    Some links:

    BlueScope Steel Australia: Avoid incompatible metals

    corrosion-technical-bulletin-ctb-12-dissimilar-metals (bluescope.com.au)

    BlueScope Steel Australia: Guidelines for using ZINCALUME® steel

    Regards
    Paul
    PS: Just on a completely unrelated note, zincalume must never be in contact with the ground. This means that it is unsuitable as a rainwater tank without a suitable lining (Acqua plate etc.). Debris from the roof (dust and dirt) has the same adverse effect as being in direct contact with the ground and corrodes the tank from the inside.
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  2. #17
    Join Date
    Nov 2007
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    melbourne australia
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    We seem to be drifting off on a tangent. The original question was whether galvanised (zinc coated) roof sheets are compatible with zincalume (zinc and aluminium) coated battens.

    I'll repost the quote I posted earlier:

    "There is a misunderstanding that Zincalume is incompatible with galvanised surfaces. Zincalume is an alloy of aluminium and zinc, which are adjacent to each other on the galvanic table. They are, as can be expected, compatible in contact."


    Note that is says they are compatible in contact.

  3. #18
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    Quote Originally Posted by jack620 View Post
    We seem to be drifting off on a tangent. The original question was whether galvanised (zinc coated) roof sheets are compatible with zincalume (zinc and aluminium) coated battens.

    I'll repost the quote I posted earlier:

    "There is a misunderstanding that Zincalume is incompatible with galvanised surfaces. Zincalume is an alloy of aluminium and zinc, which are adjacent to each other on the galvanic table. They are, as can be expected, compatible in contact."


    Note that is says they are compatible in contact.
    From Bluescope steel, which is based in Australia rather than New Zealand (not that it should make any difference).

    "
    Avoid using galvanised gutters with roofing made from ZINCALUME® steel, COLORBOND® steel or glazed tiles,"

    BlueScope Steel Australia: Guidelines for using ZINCALUME® steel
    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  4. #19
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    Nov 2007
    Location
    melbourne australia
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    Yep, we've established there's a compatibility issue when mixing zincalume and gal roofing/gutters. But not, I believe, between zincalume battens and gal roofing sheets.

  5. #20
    Join Date
    May 2012
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    Woodstock (Cowra)
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    I refer you all back to post #7
    The person who never made a mistake never made anything

    Cheers
    Ray

  6. #21
    Join Date
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    Quote Originally Posted by jack620 View Post
    Yep, we've established there's a compatibility issue when mixing zincalume and gal roofing/gutters. But not, I believe, between zincalume battens and gal roofing sheets.
    Agreed. Any risk that is there from moisture such as condensation (there is always condensation) is slight in comparison and in any event can be easily dealt with by using building paper as has already been mentioned. That is a good move anyway.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

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