Refurbishing NES console, RF shielding rust prevention - Page 1
Forum section: electronics / repair

author: Humanoid
author_rank: Regular Contributor
timestamp: April 18, 2021, 11:52:35 am
content: HelloI'm going to refurbish my old NES console and most of the refurb is pretty straight forward with cleaning the plastic parts, connectors and pcb. I'm curious how to deal with maintaining the RF shielding so it doesn't rust in the future, as right now there is lightly scattered rust on the main RF shielding pieces and the RF modulator housing.My plan is to remove all those bare metal parts and soak them in Evapo-rust (since I have some on hand) to remove the existing rust. What I'm unsure about is protecting the metal after that so it won't rust in the future.I thought of bluing the metal, but I believe that creates a layer of magnetite iron oxide, and I'm not sure if that will mess with the electronics or the soldering that is needed on a few parts.Besides that, I thought maybe oiling it lightly might work, although that wouldn't be a long-lasting solution.Curious to know if there is a known way to approach this.Thanks

author: highpower
author_rank: Regular Contributor
timestamp: April 18, 2021, 07:41:19 pm
content: I use this for protecting all kinds of surfaces.https://www.ottofrei.com/Renaissance-Wax-Micro-Crystalline-Wax-Polish?quantity=1&custcol_of_xc_size=1433

author: Koray
author_rank: Regular Contributor
timestamp: April 18, 2021, 09:31:22 pm
content: I was going to suggest any carnauba or synthetic car wax.K.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 18, 2021, 09:44:51 pm
content: The original is tin plated, I think. Might not be too far out to consider electroless tin plating -- this is, I think, usually a wipe-on formula, or it needs to be mixed from solutions beforehand.*Checking*Hmm, although, it may be that it can't be done on steel? I only see noble metals suggested... In that case, electroplating isn't much worse to be honest, but it is a whole setup you then need. (Power supply, leads and anode required. It can still be done in a wipe-on sort of way, hiding the anode in a brush soaked with electrolyte. The electrolyte should be shelf stable, no mixing required, aside from maybe a brightener additive that needs to be refreshed from time to time.)As for coatings, don't put anything insulating between the shield and PCB; the rest of the surface is open season. Yeah, the waxes are probably not bad, they won't make it look any better of course, you'll still have a pitted surface (I assume it'll be some gray ratty pitted surface left behind the rust) but it will keep water out.Be sure to wash and dry the metal very well; rust is catalyzed by water and salts, and the porous surface left behind can be very difficult indeed to clean and seal.Guessing it doesn't need to last for too many more decades, so some of these options should hold until then.Tim

author: BrokenYugo
author_rank: Super Contributor
timestamp: April 19, 2021, 01:38:30 am
content: Evaporust will turn the iron oxide to some sort of phosphate, and probably strip any remaining plating off.What I'd do is drop the parts in boiling water for about 30 minutes, then scrub the ugly spots with fine steel wool (repeat boiling if they don't go black), and oil, this will blue the rusty spots without touching the remaining plating. Same process is used to blue high dollar shotguns, which you'll often find still blue under the wood a century later.In any event you have to convert or remove the red rust and coat the steel in something else, leaving it brown and oiled won't do much.

author: Humanoid
author_rank: Regular Contributor
timestamp: April 19, 2021, 09:32:16 am
content: Quote from: T3sl4co1l on April 18, 2021, 09:44:51 pmThanks for the suggestion. Luckily there isn't bad rust. It's very small spots and some I think is just dark zinc corrosion from 30 years of the console being in a humid attic.After some further research I found that the shielding in consoles (and even arcade games) tended to have their metal plated in zinc. I looked up the zinc plating process and it's very straightforward.I need to create a zinc electrolyte by using anode and cathode of zinc in a vinegar/salt solution until it turns green (few hours). The RF shield I would wash thoroughly, may use Evapo-rust to convert the rust, but then wet sand it. After a solvent wash to dry it thoroughly (IPA, or acetone) then the shield is dipped in muriatic acid for a minute and then rinsed with water. Then the shield is placed in electrolyte with a zinc anode. I think it only needs an hour or two to get a nice plating. Might hit it with 0000 steel wool for a polish.Seems like an easy enough process. I just need to get some zinc and acid. I don't have a power supply atm, but I can use an old phone charger or something.It might be okay to add some wax to the zinc plating after and just remove it from where the PCB needs to be soldered to it. Will look into the waxes suggested by others.At any rate, thanks for the help. I think electroplating will be the best move as it's restoring the metal to what the factory did and seems easy and fun.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 19, 2021, 07:00:03 pm
content: Eh, do a test on that first. Like if it fizzes aggressively under HCl, it's zinc; slowly, tin. Or also the reduction potential, could measure that by just dipping the metal into acid along with a neutral probe and measure the voltage heh, should be pretty apparent? Bright zinc also has a bluish cast (and hot-dip has a crystalline pattern visible), I suspect it's actually tin.So, I suppose patching could also be done by just using lead-free solder and scraping it level with the surface?Tim