Lead/Oak reaction? Picture added.

[swb58]

I came across this whilst cutting my neighbours hedge, sorry I haven't got a picture.

A few years ago he had new oak gates with rail fence each side, not being a man to skimp on details he had the tops of the four posts nicely capped with lead which to my mind was a sensible approach. However, the lead on top of one of the posts has more or less 'rusted' away from underneath into into a half inch of white powder. The humps on top of the other posts look like they're going the same way too.

Is it some form of reaction? I wouldn't mind sounding a bit intelligent when I tell him about it.

Cheers.

 

[TFrench]

I'd be interested in this as well, I've got an oak gate for my drive and was thinking of capping it with lead on the exposed end grain

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[NazNomad]

I would think the oxidization of the lead was due to moisture, maybe caused by condensation under the lead itself of by the post being wet?

I don't think oak in particular would cause more or less oxidization than any other wood.

 

[Phil Pascoe]

I capped two 12" square oak posts with alloy sheet in 1975 and they're still like the day I did them. I did six large spruce ones (part of a veranda) with lead, and the last I saw them eleven years afterwards there was no sign of any deterioration - they weren't dry when capped.

 

[sunnybob]

shamelessly copied from the web....

I believe, what I have experience is an accelerated rate of oxidation, as this is a new window. The ‘scale’ needs to be cleaned off ASAP and a wax coat applied. I have some ‘Alna’ Teak wax that I think will do the trick.
Another point, Although lead is very stable in sulphuric and hydrochloric acid, it is particularly susceptible to organic acids, such as acetic acid, humic acid, and tannic acid. Lead, therefore, should not be stored in oak cabinets or drawers. If so, even small concentrations of vapours of these acids can initiate corrosion, which progresses rapidly. To be safe, lead should by stored in sealed containers or polyethylene bags.

 

[swb58]

Thanks people. Tannic acid, that would be related to tannin I suppose.

I'm part way to posting a picture, it is pretty spectacular in its own way.

 

[swb58]

Managed this much . . . . . at last!

 

[manglitter]

Thanks people. Tannic acid, that would be related to tannin I suppose.

I'm part way to posting a picture, it is pretty spectacular in its own way.

That would be why you shouldn't use steel wool on oak I guess....?

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[n0legs]

It's down to no protection and coming into contact with the moisture. Lead carbonate (I think) is the resulting white residue.
Patination oil is used on flashings, and other exposed lead, to avoid this reaction.

 

[ED65]

Yes it's lead carbonate or lead acetate, or likely a mixture of both.