Preventing corrosion of PCBs in storage

[Gregg]

Search for no-ox-id. 
https://www.amazon.com/NO-OX-ID-Compound-Electrically-Conductive-Grease/dp/B00HSW341A
It is used extensively in the high amperage DC world like telephone and wet cell lead acid battery connections.  It is like an industry standard.
It has a grease like consistency and only needs to be applied in a very thin layer.  I have seen 30 year old copper bus bars that look like new that were coated with it and were in a terrible environment of a battery room with tons of vented lead acid batteries.  It can easily be removed with acetone or 99+ IPA.   

[tautech]

I have a stack of blanks I keep in a drawer stored in a zip-lock bag.  No issue and the stock is quite old now. 

+1
I've got blanks that are at least 5 yrs old now in the plastic bags they were supplied in and laid flat and stacked in a drawer. Still look perfect. Considering one would likely do a pre-etch or a a light abrasive scrub before use there won't be any problems.
I've still got a small bit of paxolin PCB bought when I was a kid some 40 yrs ago and although it's quite oxidised (dark brown) from years of sitting on a shelf with a bit of elbow grease it cleans up OK and etches fine

[KL27x]

They come from the factory sealed in plastic. So, yeah, that would be pretty ideal. If they have corroded, already, I'd do same as I do for my toner transfer boards. Wipe on a coating of rosin flux with a paper towel. This dissolves and wipes away the oxidation. When the residual flux dries out, it seals the surface of the board fairly well against further oxidation and humidity. When the flux is thoroughly dry, it is no longer tacky. But if it isn't broke, yet, don't fix it. Seal it up and forget about it.

[MakeMonthly]

If you wanted to coat them in something that is easily removable, acrylic enamel spray paint would work.

I spray all my bare boards because I use my laser cutter to cut the traces out in the paint and then etch the board. The paint comes off just as easily as say toner transfer with a bit of acetone.

It's effort though, I'd just scrub up the boards before use. 

[SeanB]

WD40 and copper is not a good idea, it will result in a lot of green crud with time. It is noted in the data sheets not to use on brass, as it will damage it long term. wWorks fine on steel, keeping it reasonably free of corrosion in a semi controlled atmosphere.

Best is sealed in a non permeable laminated vapour proof bag, with a sachet of desiccant in there, and wrapped with each sheet of PCB in acid free kraft paper, all with a overpack inside of plastic lined wax paper. That will, provided it is not opened, or is resealed very fast after a careful open ( make a long end so you can do a number of seals before needing a new bag) and quick removal of the needed quantity, last for decades.

Another method is to dip the clean boards in hot paraffin wax, and then into a waxed paper cover, and then place the whole lot in more waxed paper and then finally in a vapour proof bag. Nuts , bolts and complete delicate assemblies preserved that way come out looking like new after a quick boiling in solvent to get the wax off.

[Rudane]

Yes, silver is good too! However, I've noticed not all manufacturers have the option for silver.

[Lomax]

Search for no-ox-id. It is used extensively in the high amperage DC world like telephone and wet cell lead acid battery connections.  It is like an industry standard. It has a grease like consistency and only needs to be applied in a very thin layer.  I have seen 30 year old copper bus bars that look like new that were coated with it and were in a terrible environment of a battery room with tons of vented lead acid batteries.  It can easily be removed with acetone or 99+ IPA.

Vaseline. You're talking about vaseline.

[helius]

It's actually the product formerly known as Cosmoline, which consists of petrolatum with fumed silica and other agents.

[Lomax]

WD40 and copper is not a good idea, it will result in a lot of green crud with time. It is noted in the data sheets not to use on brass, as it will damage it long term. Works fine on steel, keeping it reasonably free of corrosion in a semi controlled atmosphere.

Thank you. Inappropriate uses of WD-40, and its derivatives, is a pet peeve of mine - not least since I once spent an entire weekend clearing out gummed up (what I assumed to be) WD-40 from the (Alps) faders and pots on a 32 channel mixing desk with dual swept mids, four sends, and eight subs. My fingers hurt just thinking about the amount of knob-twiddling that involved. Some of the pots in particular, had gummed up so hard it was impossible to turn them until they'd been soaked for an hour. I used up a whole tray of alcohol spray bottles, and had to remove each of the channel strip PCBs from its front panel - that's something like 14 pots and one fader per channel, times 32, plus the subgroups and masters - all of them with their own fiddly lock-screw and fixing nut. I still have nightmares about it, but the exercise was a success in that the console became fully functional.

Best is sealed in a non permeable laminated vapour proof bag, with a sachet of desiccant in there, and wrapped with each sheet of PCB in acid free kraft paper, all with a overpack inside of plastic lined wax paper. That will, provided it is not opened, or is resealed very fast after a careful open ( make a long end so you can do a number of seals before needing a new bag) and quick removal of the needed quantity, last for decades.

Another method is to dip the clean boards in hot paraffin wax, and then into a waxed paper cover, and then place the whole lot in more waxed paper and then finally in a vapour proof bag. Nuts , bolts and complete delicate assemblies preserved that way come out looking like new after a quick boiling in solvent to get the wax off.

It was exactly some kind of spray on wax I was imagining would be the right thing; (relatively) easy to remove, solid enough not to smear onto everything around, and (probably) solderable through, in case you haven't cleaned it off 100%.

[Lomax]

Full disclosure: I live on a boat. Or at least I will be, once the shipyard tires of pillaging my bank account.

[Ian.M]

You are FUBARed - your *ONLY* long term chance would be the foiled mylar bags and an Oxygen Adsorber.   Every copper surface on a boat eventually goes black, green or crumbles away!

Assuming you are on salt water, SeanB's suggestion may work if you can go inland a few miles to get away from the salt in the air to initially clean the boards and pack the bag, but if you open it on board, chlorides will get in for certain, and you'll also get sulphur compounds and salty oily particulates from traces of your own or nearby diesel exhaust that have blown into the cabin recently.

[KNSSoftware]

all these modern techniques - just ask your grandma; bury them in rice!

[mmagin]

CorTec has a line of VpCI products that can be used to prevent corrosion in storage (films, papers, and satchets) but I don't know whether there is a distributor in the UK.

This is probably the best answer, as far as something that's actually effective and that you won't have to clean off afterwards.  There are various brands of vapor-phase corrosion prevention products, some may be specifically for steel, but many of them are sold for multi-metal use.