Silicon!

[simonwood]

Hi,

Is it possible that silicon sealent can corrode s.steel/steel/lead?
This is high quality sikaflex marine sealent.

I think no, silicon is very very innert except on some plastics it make it brittle.

What do you fellow friends think?

cheers aye!


Simon


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[spynappels]

Most silicon sealants release some form of fumes when they cure, eg high temp silicon releases acetic acid fumes when it cures, but once this is finished, there is no problem. In any case, the fumes released will be minimal and should not cause any problems. Were surfaces perfectly clean and dry when the sealant was applied? Else moisture was locked in and would corrode its way out...

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[VicS]

Re: SILICONE!!!!!

Silicone sealants release ethanoic acid, aka acetic acid, while curing. You cannot fail to notce the vinegar like smell. While only a weak acid it can attack some metals. Many years ago a friend and I sealed a pair of deck lights with a silicone only to find next day that all the plating had been stripped off the reflectors. More recently a former colleague found to his cost that it attcked lead flashhing.

I cannot say for sure if this applies to all silicone sealants and suggest you consult the manufacturer's data sheets.

I doubt whether stainless steel is affected but some attack of iron and steel is likely.

PS SILICON, as opposed to silicones, is a hard brittle non metallic (some will say semi metallic) element. It is the second most abundant element occurring as silica and many complex silicates. It is no good as a sealant, as oils, as synthetic rubbers or for breast implants, but finds considerable use in micro electronics.

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[snowleopard]

silicone gives off acetic acid. it is better to bed stainless fittings with polyurethane sealant. all the types of sikaflex i have met are polyurethane, not silicone. silicone is easy to detect by the vinegar smell.

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[burgundyben]

if its a sika product are you sure its silicon? most of the sika range are polyurethane I thought? (I am quite possibly wrong about this)

have you had a particular instance of corrosion?

<hr width=100% size=1>I didn't knacker TCM's copper it was Trazie

 

[simonwood]

Hi guys,

Nope there is no sign of the silicon effecting metal, it all rather complicated, i'll let you know why i ask in a few weeks - all rather "top secret" at the moment, but it will be worth the wait i promise!!!

thanks guys

si

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[silverseal]

Stainless steel is attacked by weak organic acids, the worst being citric acid. Acetic acid is used in the curing of genuine silicone sealants, and I am not surprised that some tarnishing may take place

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[LittleShip]

I made a conscious decision not to use silicon on the boat, but to use the marine based equivalents. IMHO I don’t feel that silicone is a good choice in the marine environment when better (more expensive) products are available. I have always found that cleaning it off afterwards is a pain and I hate the smell???? The only use I have found it good for is a thin covering on fittings before refitting hoses on the engine!!
Only my opinion as I know many out there use it.


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[greeny]

When you use any type of sealant or sealing tape on S.S. you should ensure that the surfaces are well cleaned of any salt deposit first. It's not the sealant that will cause the problem necessarily but a process called "chloride pitting" which is caused by the salt and accelerated by the oxygen depletion under the sealant. I don't profess to fully understand the chemical reactions taking place but this is a common problem in the offshore industry where S.S. tubing can be corroded right through in areas under clamps or where tape has been applied and the air excluded. I'd be more concerned with this than the silicon itself.

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[gibbo26]

There are 2 types of silicon sealant, the common type which smells of vinegar when curing and the other type is called Neutral cure silicone, which has a longer cure time (easier to smooth off) and does not corrode metal or damage plastic.
Great for use on boats!

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[MainlySteam]

<<<This is high quality sikaflex marine sealent.>>>

If it is Sikaflex then I believe you can be quite confident that it is not silicon. It will be polyurethane based.

If it is silicon then I think that you can be quite confident that it is not Sikaflex nor, quite likely, any other Sika product.

John




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[MainlySteam]

<<<Is it possible that silicon sealent can corrode s.steel/steel/lead?>>>

Think that it is extremely unlikely. I see silicon sealants used to seal the mounting flanges of big water jet units from at least one manufacturer to aluminium hulls with no problem.

If it is not silicon, but is actually Sikaflex, then you have no problem with corrosion of those materials either.

Note that I am not making any comment on the applicability of either product for whatever it is that you plan on doing with it. Am just commenting on whether the sealant will react with the metals you state.

John

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