Water proofing metal
January 13, 2012 2:00 AM   Subscribe

I want to collect small amounts of liquid through a sheet metal funnel, but the liquid sticks to the walls, so I need to make them water repellant. I thought about using one of those nano sprays, but don't know if they actually work and which one would be the best. Any ideas?
posted by SweetLiesOfBokonon to Home & Garden (14 answers total)
How about those sprays or wipes that are meant to help rain run off your car windscreen? I don't know if they'll work as well on metal. You'll also have the issue of contaminating whatever it is you're collecting. Googling 'hydrophobic coating' will help you.
posted by dowcrag at 2:12 AM on January 13, 2012

I'd start trying scotchgard, but similarly I don't know how it'd adhere to metal.
posted by pompomtom at 2:28 AM on January 13, 2012

Maybe regular car polish would work?
posted by Harald74 at 3:19 AM on January 13, 2012

How about non-stick cooking spray?
posted by Blazecock Pileon at 3:31 AM on January 13, 2012

Does it have to be metal? How about teflon funnels?
posted by Chocolate Pickle at 3:36 AM on January 13, 2012

It has to be metal, the funnel is part of a metabolic cage. I am collecting urine from lab mice with those. And of course it should not pollute the sample, I need it for analysis, Na/ K/ Mg/ Kreatinin etc.
posted by SweetLiesOfBokonon at 4:19 AM on January 13, 2012

You might try stuff called "conformal coating". It's generally used in the electronics industry to protect circuit boards - you dip or paint the board and the material flows around the circuit components and then sets. The coating is designed to repel water and contaminants.

You might also try waterproofing sprays for outdoor equipment (check REI or similar) or refinishing sprays for recoating Teflon cookware.
posted by backseatpilot at 5:59 AM on January 13, 2012

Does it have to be metal? Could you make a PTFE (teflon) liner? Premade PTFE funnels and and sheet are available. PTFE is a bit hard to work, but I've used it for similar things. A cheaper alternative is HDPE. More stuff will stick to HDPE than PTFE, but it's better than metals.

Personally, I would not trust a commercial coating product without a lot of testing.
posted by bonehead at 7:04 AM on January 13, 2012 [1 favorite]

Maybe coat the funnel with plastic wrap, which is hydrophobic. If you have to use multiple sheets, be sure to shingle them so the urine stays on the correct side.
posted by exogenous at 7:10 AM on January 13, 2012

Most plastic wraps are LDPE.

Another option might be wax. If Parawax film is compatible with your requirements, you may be able to buy some lab-grade wax and melt coatings onto you funnels. Thermo Fisher sells a half kilo of refined wax for about $50. This would be much cheaper than PTFE.
posted by bonehead at 9:18 AM on January 13, 2012

Ah, if you don't want to pollute the sample, don't use Rain-X (the windshield stuff). It comes off.

Maybe you could smear the interior with a thin layer of silicone sealant? I'd get the kind where you have to mix components together rather than the stuff like aquarium sealant that relies on solvents to cure, because the solvent might take a while to work their way out. Silicone is very nonreactive, won't leach anything once it's cured, and has a high contact angle, so it should suit your needs unless the material needs to be strong enough to withstand mouse teeth.
posted by tchemgrrl at 10:18 AM on January 13, 2012

If you're thinking of smearing with silicone sealant, why not use silicone spray?
posted by Mike1024 at 5:05 PM on January 13, 2012

A silicone spray will involve a solvent, which will contaminate the experiment.
posted by Chocolate Pickle at 7:31 PM on January 13, 2012

I had a metal fitting coated by Aculon. It's extremely effective, water beads up on it better than on the Teflon gaskets that it has. It was excitingly expensive though, on the order of $500 for a 8 inch long stainless steel fitting.
posted by Confess, Fletch at 7:37 PM on January 13, 2012

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