Bought a Metcal PS2E, it's got this weird powder inside. - Page 1
Forum section: electronics / general

author: poodyp
author_rank: Regular Contributor
timestamp: November 28, 2012, 02:29:13 pm
content: So there aren't many Metcal teardowns that I've seen, so I wanted to see what was inside mine.Powder apparently.It's all over the transformer too.So any idea what this stuff is? Galvanic corrosion? Crystalized flux fumes?Everything else looks spotlessexcept maybe where the stuff got shifted during shipping. The thing works perfectly so I'm not too worried.

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 28, 2012, 02:42:18 pm
content: It looks like corrosion from the metal plate the transformer is mounted on, almost if there has been some water in there for a while...

author: SeanB
author_rank: Super Contributor
timestamp: November 28, 2012, 04:00:28 pm
content: The aluminium has been exposed to salt water at some point, which has caused this corrosion to occur. Best way to treat it is to strip off all other material ( steel transformer etc, then wash it and then immerse for a few seconds in a concentrated sodium hydroxide solution ( use gloves, drain cleaner flakes burn) to strip off the oxide layer. It will bubble and fizz and go dark. Rinse in cold water then dip for a minute or two in white spirit vinegar to reform the oxide layer, then rinse and dry. Then spray with a clear lacquer or spray grey primer and satin black paint to get a smooth non gloss finish.

author: ftransform
author_rank: Frequent Contributor
timestamp: November 29, 2012, 04:45:02 pm
content: that my friend is the french connection.get yourself a rig and enter the land of nodheroin filled capacitors

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 29, 2012, 06:04:22 pm
content: Could also be the result of spilt liquid flux - maybe more likely than seawater for a soldering iron.

author: SeanB
author_rank: Super Contributor
timestamp: November 29, 2012, 06:19:14 pm
content: You find it under the edges, so likely it was contaminated before assembly, possibly during shipping if it got exposed to acid rain or other industrial pollution in an open container.

author: poodyp
author_rank: Regular Contributor
timestamp: November 30, 2012, 08:47:08 am
content: I wonder how the entire bottom is so messed up, but the rest of completely spotless. It's like the bottom was removed, soaked in water, and then put the transformer and everything back.I tried cleaning it with some drain cleaner, but I'm guessing it was too dilute (only 1-5%). Here's what I got after an hour:I'll get some pure sodium hydroxide and try again.

author: muvideo
author_rank: Frequent Contributor
timestamp: November 30, 2012, 09:19:05 am
content: Quote from: poodyp on November 30, 2012, 08:47:08 amHello, maybe it's a silly question, but that piece seem die-casted, are you sureit's aluminium alloy and not zinc alloy (some zamak) ?If so probably the NaOH stripping procedure will not be that effective.Zama will have a density similar to steel, while Al will have less than half.If it's Al, if you have access to nitric acid (not easy but maybe you can)the NaOH+distilled water+HNO3 procedure is very effective in restoringaluminium parts. Some Al alloys work better, some become darkafter NaOH. The NaOH becomes hot during the process and aftera while starts eating fast, careful with threads.Fabio.

author: SeanB
author_rank: Super Contributor
timestamp: November 30, 2012, 04:31:43 pm
content: Works great on corroded or worn coloured aluminium parts, though you only dip for a few seconds then remove and rinse FAST. Make sure you get all the caustic soda off. For screw threads it is easy to just fill them up with grease, it will be eaten up by the NaOH, but will survive for the few seconds needed.

author: poodyp
author_rank: Regular Contributor
timestamp: December 01, 2012, 01:51:11 pm
content: Unfortunately nitric acid is a little hard to get. It'd be fun to have some to play with, but $63 for 500ml is too much. I could distill it but that's also somewhat expensive and I would love an awesome Liebig Condenser, but don't have one currently.Anyway, I'll try with just the sodium hydroxide and see how that works. I don't want to go through a lot of trouble just to clean off the inside of one piece. Even if the entire bottom falls apart, for $30 I won't be upset.

author: SeanB
author_rank: Super Contributor
timestamp: December 01, 2012, 02:09:18 pm
content: I just use citric acid, though normally I use abscorbic acid, as it is easily available at work as expired stock.

author: Shock
author_rank: Super Contributor
timestamp: December 01, 2012, 06:42:57 pm
content: Don't mean to thread hijack but as the mystery of thecocaineoxidization looks near resolved.Question to you SeanB... or others who have come across this.I have a Fluke 73 which needs restoring and the test lead sockets are semi corroded.I'm hesitant to use the new leads on it before I remove that corrosion.What would be the best method to remove that corrosion and to preserve a good electrical connection?

author: SeanB
author_rank: Super Contributor
timestamp: December 02, 2012, 04:47:38 am
content: Pipe cleaner with Caig deoxit will work well.

author: Shock
author_rank: Super Contributor
timestamp: December 03, 2012, 08:29:16 pm
content: Looks like the cheapest I can get the plain Deoxit is about $30 a can here.I have electrical contact cleaner, alcohol, penetrating oil lubricant (WD40, if needed), vinegar and bicarb soda and such.Various household type cleaners. Silicone spray (have to see if its conductive).Is there any other method that will work?How about citric acid in this case as well? Can also use some cola (phosphoric acid).From what I understand of my basic chemistry is I first need to dissolve the oxidization.Then I need to clean/flush that off with contact cleaner or alcohol.Then use a somewhat conductive lubricant to protect it.

author: SeanB
author_rank: Super Contributor
timestamp: December 03, 2012, 08:38:34 pm
content: Contact cleaner, after working through with the WD40 on a few cleaning pipe cleaners.

author: ptricks
author_rank: Frequent Contributor
timestamp: December 03, 2012, 09:19:09 pm
content: Check the transformer for leakage currents. The last time I saw something like that it was from an aluminum heat sink that had stray currents flowing through it. If the casing is grounded and there is stray current flowing through , that will increase corrosion rates x10.

author: Shock
author_rank: Super Contributor
timestamp: December 03, 2012, 10:01:26 pm
content: Quote from: SeanB on December 03, 2012, 08:38:34 pmCheers I'll give it a try.

author: sotos
author_rank: Frequent Contributor
timestamp: December 04, 2012, 01:29:23 pm
content: After cleaning, try this it’s incredible.ACF-50 anticorrosion and protection of electric – electronic gear or pcbs.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 04, 2012, 09:41:54 pm
content: Personal I would have used a brass wire brush and spent a couple minutes cleaning it and then used self etching primer with a top coat on it and be done with ...

author: ptricks
author_rank: Frequent Contributor
timestamp: December 05, 2012, 12:28:21 pm
content: You can also use epoxy paint. Epoxy paint comes in spray paint type cans but like the name suggest contains epoxy also, it dries hard and is often used to touch up appliances that have a baked on finish.http://www.krylon.com/products/epoxy_enamel_paint/

author: robrenz
author_rank: Super Contributor
timestamp: December 05, 2012, 02:26:35 pm
content: For mechanical cleaning of aluminum, glass bead blasting cant be beat. Most automotive machine shops will have one.