More questions for the boffins

[Michael Rogers]

Me again, apologies if I am being irritating.

Q1  PTFE is 'nonstick': but is there an adhesive which will stick it to other things, and/or to itself?

Q2  I would like to take my angle grinder to the bulb on the end of a folding grapnel anchor, so that it fits snugly into the anchor locker in the bows of my Trouper 12 dinghy. A couple of mm of flattening of one side would make all the difference to the fit, but this will take off the galvanised coating over a smallish area. What's the best way of replacing the effect of the zinc and protecting this 'bald' patch so that it doesn't rust?

Thanks again, help much appreciated.

Michael

[Jeremy]

The reason that PTFE is non stick is to do with a property called surface energy.  Some plastics, in particular, have a very low surface energy and this makes them particularly difficult to bond to, PTFE probably being the hardest.  There is a fix, and that's to use either a special low surface energy adhesive or to mechanically fasten the PTFE.  There are special cyanoacrylate adhesives that are supposed to bond to PTFE but my limited experience suggests they don't bond that well in practice.  The best way I found to bond some PTFE wear strips in place was to use some special double sided adhesive tape, intended for bonding low surface energy plastics.  Unfortunately I can't remember the make of it, as it was some years ago, but a hunt around on the web might find some.  

You can get cold galvanising paint that can be very effective.  I've used Galvafroid in the past and found it to be quite remarkably long lived - the once rusty padlock that secures my shed was given a coat of it around 15 years ago and there's still no sign of rust coming through.  It will get worn off on an anchor, but with luck the protection from the surrounding galvanising plus the Galvafroid should be OK for a season or two before it needs a touch up.  Alternatively, you could get the anchor re-galvanised.  It shouldn't cost much as they usually charge by the area of the object.  If you can find a maker of farm gates, hurdles etc nearby then it might be worth having a word and asking if they could slip it in with the next batch they send away for galvanising.

[momist]

+1 for Galvafroid.  I used that on my exposed garage bolts 25 years ago and it still looks like I painted it on a few days ago.  As Jeremy said, it will wear off on an anchor, but since you will use so little from the tin in the first place, the tin should  last you a lifetime.

Sticking to non-stick is an oxymoron in my view.

Ian

[Michael Rogers]

Not just in your view, Ian, by definition it's an oxymoron: you're quite right. I think a few carefully deployed fine pins are called for - it's a non-marine situation related to the lighting board mounting (I won't elaborate, it's not that interesting). On the other matter, Galvafroid sounds like the business. Thanks - and to Jeremy.

Michael