Cleaning Nickel Plating on BNC Connectors

[garrettm]

I have a Racal Dana 9300B that I'm restoring which has green nickel compounds on the AC input and DC output BNC connectors.

In the past I have used a hot (i.e. boiling) dilute ammonia solution to quickly clean nickel (by forming a water soluble Ni complex). This, however, removes the nickel compounds and thus exposes the brass base metal underneath the corroded plating. In summary: it works, but looks like crap.

A similar process involving a mild abrasive like sodium bicarbonate paste or those off-white buffing disks for small rotary tools also cause the same problem: removes the corrosion and exposes the brass base metal.

Ideally, I would like to reduce the oxide/hydroxide/halide (or whatever!) compounds to minimize pitting and exposing the brass.

I've attached some close ups of the rear connector showing the corrosion. I believe that if I can identify the specific type of corrosion I'll have a better chance at reducing the nickel with minimal pitting.

Since almost all the obvious types of nickel corrosion are green--and my overwhelming inexperience with the subject--leaves me to assume what I'm seeing is nickel chloride or hydroxide. Can anyone more knowledgeable confirm this and maybe guide me to a satisfactory cleaning process without involving exotic compounds?

I suspect that a combination of either a weak organic acid (ascorbic, citric etc.) or base like sodium bicarbonate (depending on the specific anion I need to safely remove) and electrolysis I can possibly achieve this.


P.S.

For the adventurous reader, here's a pdf about Nickel and its various compounds. Table 1.1 gives a good overview of all the various ways that nickel can become corroded (oxides, sulfides, hydroxides, and salts).

https://web.archive.org/web/20220213203937/https://monographs.iarc.who.int/wp-content/uploads/2018/06/mono100C-10.pdf

[coppercone2]

Lol, I give them a polish with chrome polish on a soft buffing wheel using the dremel or preferably a slower tool. On the inside I also use chrome polish on a Q-tip.. inserted into a dremel. I saw robrenz cut a special felt insert for the inside of BNC connectors so it can be polished all in one go. Be sure to trim your polishing thing to fit correctly (not the blunt nose of the q-tip for the end of the connector interior)

For the inside receptical I put deoxit 100% solution on a micro-q tip (from Caig) and manually scrub it until it clean, leave it for a few days then redo it. You can also get a micro nylon pipe cleaner, cut it short, put it in a dremel and give it a good scrub down. There is ALOT of shit in the inside pin of the BNC connector on old corroded crap.

You can put them in a ultrasonic cleaner for a while before you polish to remove some crap that can scruff the surface. You might want to wipe it down by hand with polish and throw away/wash the rag at first before using high RPM tools to reduce scratching from large surface inclusions. For the interior, manually swirling a Q tip dipped in polish in there will do 'gentle removal of heavy objects' before you go into rotary polishing.

I never managed to expose base metal on a BNC connector.. usually those polishes are ultra fine, and the coatings are thick on decent connectors (before china).


I would LOVE a dip that makes it decent, but I never got a good feel from the connectors without repolishing them. I don't like high insertion force on my stuff, easy to ruin cables that way. You can try ultrasonic baths with the anti-corrosion chemicals but I don't see it being too much better.


Electropolishing is a interesting option of course.. but my attempts have been trash. As far as cleaning crap up without scrubbing, electropolishing (as seen for post stainless welding cleaning) looks like the only method that I ever saw that I think would maybe work if you got it right.


I believe rob-renz found Si-chrome chrome polish to work good, I just used some other stuff.


If you want to try electropolishing, try starting here


Not that easy though, lots of crap to figure out.. but I do have enough connectors that it might be profitable to learn how to do that right... applied science guy knows alot of chemistry and even so his aluminum got pitted, which would be a big problem for a connector...


I have this gut feeling that... if this was easy, there would be alot of jewelers that would go out of buisness. Those people are super paranoid about leaving the surface of their work intact but you still see them go for the polishing compounds. Electric and chemical polishing are great when you can do R&D to tune up the process to save costs in a industrial setting.. but it hardly seems that there is a one fits all solution to these problems. (they have very strong skill and know how about how much pressure, speed, duration to use for their restorations).

Keep in mind that there are various grades. I.e. red rogue is medium grit polish, while green rogue is very fine polish, and it also has to do with correct choice of friability, hardness and structure of the abrasive medium. The only thing I would worry about really removing alot of material way too fast is diamonds, they eat metal... but perhaps if you carefully use the absolutely finest diamond paste you can find, it would not be so bad.


I think I tried baking soda + flour a few times and it was not as gentle as people make it out to be when I was cleaning the exterior of my gas welding equipment, green rogue actually made alot nicer finish that looked less scratchy.

[garrettm]

I never managed to expose base metal on a BNC connector.. usually those polishes are ultra fine, and the coatings are thick on decent connectors (before china).

It depends on the thickness of the plating. For small hardware (nut, lock washer etc.) used to mount front panel switches I have seen the brass exposed during cleaning. And the same goes for the switch lever itself. These tend to use very thin coatings of nickel or were very badly corroded.

To be honest, I haven't tried cleaning any BNC connectors to date, as I usually just replace them. However, this Racal Dana unit uses an uncommon insulated BNC connector which forces me to clean it.

I tend to avoid mechanical techniques since 1) they are messy and 2) its significantly more work and time intensive than using chemical methods. It's also less effective at cleaning in hard to reach places, which robrenz found out by having to make his modified buffing attachment. But he is a machinist, so I don't begrudge him for putting his extensive life experience to work in making cool adapters to straighten and clean BNC connectors.

Deoxit really isn't needed for gold plated beryllium copper center contacts. That said, PPE (polyphenyl ether) lubricants can extend the life of the connector’s center contact/plating. Though you are better off buying generic, electronics grade PPE than using one of Deoxit's "special" formulations.

https://en.wikipedia.org/wiki/Polyphenyl_ether#Electronic_connector_lubricants

https://web.archive.org/web/20210226081714/http://www.chemassociates.com/products/findett/PPEs_LubEng.pdf

[coppercone2]

well show me results of a good chemical dip clean that also have a good connection feel (smooth) and I would have no problem switching over, its not I like doing it. Its dusty, loud, labor intensive and generally painstaking.

Like if you read what people write about Tarn-x (supposedly a silver specific cleaning dip) and it gets dissed pretty hard.. thankfully for silver the rub on platings work great to restore them. I tried it on some connectors and spoons and they look like ass compared to kool-amp silver plating powder (which is also alot of labor intensive scrubbing).

I would actually recommend over polishing and replating stuff that is easy like screws. Its the geometry of the BNC that makes it a pain in the ass.

For alot of screws I actually like to just paint it black with gun blue and grease them up with deoxit mixed with some oil, when they are totally fucked up I mean. Pin vise + dremel stainless brush wheel followed up by dip gun blue. So long it stays inside its OK but if you leave it in a place with temp swings and condensation, it won't stand up to that very well. If you do it, SOAK them in oil in a little beaker when you are done bluing, and heating the whole thing up does not hurt things either (hot plate). I do complete disassembly, process all the screws, soak over night and reinstall 2 days later when I am done scrubbing the tobacco and whatever off the PCBs (audio amps  )


There is also a fixture you can build for cleaning screws.. so obviously the threaded part its OK to grip it in a pin vise to clean the head, but how do you do the other end? Well.. if you take a nut and the right sized washer, you can braze the nut to the washer and then put the screw in it so it sticks out the front of the washer and press it into place with a bolt so you can get a good grip on the screw and clean the tip of it. Trying to grip screw heads in pliers or vise grips before polishing or cleaning is a great way to lose screws.

Also if you watch watch cleaning/repair/restoration videos, they might give you a few techniques appropriate for electro mechanical devices and stuff inside of electronics.

As for deoxit, stuff that I left it on for a long time that is difficult to clean eventually builds up some kinda green crap, as per the deoxit documentation, that wipes off easily with a brush and stays off (center contacts are kinda impossible to clean).

[TERRA Operative]

If BNC's are dirty and isopropyl alcohol doesn't fix it, I give them a light brush with a brass wire brush (the toothbrush sized ones from the dollar store) to remove the crusty stuff, followed by a polish with those jewellery polishing cloths you get also from the dollar store.

Works well for me...

[garrettm]

Works well for me...

I admit that a light brushing would probably do the job in this instance. For significant corrosion, however, mechanical cleaning is not a viable solution.

Below is a type-N male-to-male barrel connector for an HP network analyzer that is made from stainless steel and nickel coated brass. The foam inside the accessories box degraded overtime into a sticky goo that adhered to the surface of all the accessories. This goo attacked both the stainless steel and nickel coatings of the accessories. The attached photo shows what a light cleaning with a soft cotton buffing wheel did to the surface (removing only the visible corrosion).

Notice the pitting and white hazy surface. Polishing the cleaned surface will reduce the haze but it cannot fix the pitting. Had I used a reduction process, rather than naively removing all the corrosion, I likely could have had a much better result. It still wouldn't be perfect, but there is a reason coin collectors don't grab a brass brush to clean off all the grit on an old coin.

[TERRA Operative]

If a connector is at the point of the plating flaking off and exposing the underlying metal, I just replace it.
I don't have equipment with unobtainium connectors though, so I don't need to keep the original connector if it's beyond a general cleaning.

[jpanhalt]

In response to your original question, you cannot reduce corrosion on metals and get any sort of satisfactory finish.  Corrosion disrupts the crystalline structure on a metal's surface.  The only option is to remove, polish, and replate. 

Of course, for light corrosion, simple removal is sometimes adequate to restore a satisfactory finish.  Nickel is less conductive than brass, so removal won't have any effect on resistance.  I would consider doing one of two things:
1) Light polishing to get good electrical contact.  Then live with it. 
2) Remove the BNC connectors, remove the all pating, and replate with either nickel or silver.  Bright silver is probably easier to do.  Or, buy new connectors.

For me, I would stick to the first option.  For a restoration once of a small airplane, I removed the ash trays, and did the whole remove, polish and plate cycle.  Of course, they were easy to remove and I had access to a chemistry lab for the cleaning and plating.

[Wallace Gasiewicz]

About nickel plated screws... years ago I helped restore an American LaFrance fire truck, 1923 model I think.
There were big nickel plated screws on various parts including the 900 cubic inch engine. We found that polishing new stainless screws with a polishing wheel made the screws look very close to the original nickel plated screws. Even the judges did not notice...

[coppercone2]

I did get a plating pen recently, I kind of wonder what it does with the electro cleaning solution (would need to mix it up)