Mix
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 posted on 1/10/03 at 09:01 AM |
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Corrosive sealers
Don't think this has been aired here before but am prepared to be shot down in flames.
Some sealants have an acidic content and as such may induce corrosion, especially when used with light metal alloys, (aluminium, magnesium etc.).
Whilst not a great cause for concern if you have already used one it may be of benefiet to point out to future uses that sealers with an acid content
usualy smell of vinegar, (acetic acid).
You pays your money and takes your choice, As they say
Mick
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David Jenkins
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| posted on 1/10/03 at 09:07 AM |
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I believe that you are correct - general-purpose domestic silicone sealant does contain acetic acid. PU sealant doesn't, or you can buy
non-acid silicone sealant.
However, I don't know just how bad it is for causing corrosion.
David
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kingr
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| posted on 1/10/03 at 10:05 PM |
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Acetic acid, also known as vinegar (hence the smell), I shouldn't worry about it unduly, I can't see it's gonna strip your chassis
too quickly.
Kingr
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GasGasGas
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| posted on 3/10/03 at 08:37 PM |
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Sealants
Silicon acetate or the smelly silicon uses acetic acid as a SOLVENT !-- But what happens with solvents?-- thats right they evaporate--so as the
sealant hardens the acid content lowers so therefore no corrosive action, also the acid can have the benefit of mildy etching the surfaces being
adhered.
Non smelly silicon cures by the absorbtion of air, same as polyurethane sealants.
Silicon acetate (smelly) offers a high strength bond with little movement while nuetral silicons (non-smelly) offer a good bond but will allow a lot
of movement.
So if you want to use silicon as a glue use silicon acetate (vinegar smell) .
P.S. silicon acetate is normally by far the cheaper product.
If you want ultimate bond strength use PU or polyurethane (sikaflex) sealant, it too has two movement strengths but the high mod (low movement) on a
properly pre-pared surface will offer a joint that few other products can beat.
You pays your money you takes your choice !!
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Mix
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| posted on 4/10/03 at 04:29 PM |
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Mmmm!!
That'll be why we've been warned against them and have stopped, are stopping using them in the aluminium alloy oriented aircraft
industry.
As I implied before, the consequences will not be great and I am only passing on info for others to do with as they please.
Mick
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