L&R Extra Fine Solution stripping nickel?

[spectre6000]

I ran a movement through my cleaning routine last night, and I was a little surprised at the end to find about half the plating was removed from the main plate! I thought the whole point of the L&R Extra Fine Watch Cleaning Solution was that it was safe for watch bits... I'm not one to blame others for my mistakes, however, so help me figure out where I went wrong.

This was the third movement through no more than a 100mL volume of cleaning solution. The first went through fine; similar overall construction and material to the last. The second was a thoroughly beat unjeweled and oxidized mess of a movement. Brown brass plates. After that movement, the cleaning solution had taken on a noticeable green tint, which I assumed to be copper oxide from the oxidized brass. Intuitively, I assumed it to be particles in suspension, but in retrospect nothing ever precipitated out so it's possibly a chemical change in the solution.

The first rinse also affected a change during this process. I think it wasn't until part way through cleaning the not-junk watch after the junk watch, but it got slightly cloudy. I haven't checked yet to see if anything has precipitated out in any of the jars, but I'll make sure to take note the next time I'm in the vicinity with some bandwidth.

My cleaning process is 10 minutes in the heated ultrasonic in each of clean, rinse 1, and rinse 2 where the cleaning solution is as stated above and the rinse solutions are L&R #3. That's 30 minutes total in the ultrasonic for every hard part.

I'm pretty sure I spoiled the cleaning solution with the dirty and oxidized junk watch. What's the deal exactly? I'm banging around right now making stupid mistakes, and this is clearly one of them, so I want to make sure I take away the right lesson.

[spectre6000]

I went in there and took a look at things after any precipitates have had a chance to settle out over night. The cleaning solution is forest green (it starts out a straw yellow), but clear. Rinse 1 has cleared up, and there's a light gray sediment on the bottom; undoubtedly the nickel from the main plate.

Also potentially notable is that no other plates, bridges, or cocks seem to have suffered similar damage. The main plate is substantially stripped of nickel, and ONLY the main plate. It was cleaned at the very end, and the solution temperature was higher, but we're talking a max of 50°C and a minimum of 20°C or so (room temp).

[CaptCalvin]

I had the same experience.

I find that it already starts to oxidize some things even at 5 minutes. 10 minutes is much too long. I wouldn't submerge parts in this solution for longer than 3 minutes. All other cleaning/rinsing fluids that I have say 3-5 minutes on the labels. The Extra Fine, the most corrosive watch cleaning fluid that I've ever used, is for whatever reason the only one that does not print this guideline on the label.

Edited June 24, 2020 by CaptCalvin

[JohnR725]

16 hours ago, spectre6000 said:

My cleaning process is 10 minutes in the heated ultrasonic i

I think you've beaten everyone else out for dramatic effect we've discussed this before others have noticed similar problems. The cleaning solution is designed to remove  the old oils etc. and brighten the plates by removing oxides. The problem is go past a certain point in time it starts to etch. The blue color is because the ammonia has dissolved the copper out of the brass.  I notice you heated the solution this is going to make much more dramatic etching effect.

I notice these painful lessons are the ones we really learn. As a student in school the cleaning machine had a timer 10 minutes I frosted a pocket watch. Fortunately I could polish the plates it looked okay but I never did that again. In the second school they actually taped the machines timers so you could not go over four minutes for the cleaning. 

So personally for me I don't go over four minutes for the cleaning solution at room temperature. I tend to worry less about the rinsing solution as it doesn't have the aggressive chemicals in it but I don't think it really likes to be hot either so maybe try doing your cleaning at room temperature and cut the times down considerably.

 

 

[rodabod]

Some plates are vulnerable to this. Ammoniated solutions will get under thin playing and eat brass. And ultrasonic only exacerbates this. 

[spectre6000]

OK. So, correct, no stated time from L&R. Also, my guidance for the ultrasonic timing was "not too long", which obviously isn't helpful if you don't have any data points to work from. I picked ten minutes because the manual for the machine says to give it a rest after 30, and that was my solitary datapoint for "too long". Ten was a nice round number. It worked fine until it didn't. I'll drop that going forward.

I figured the green was dissolved copper, but given how rough the unplated brass movement was that caused it, I didn't give it a second thought. I also don't have much in the way of data points for how long cleaning solution lasts... Obviously it depends on what goes into it, but in general terms, what should be expected?

Lesson learned, shorter time with the cleaning solution. Shorter time in the ultrasonic. 4 minutes has been indirectly recommended for some type of machine (ultrasonic or spin?). What is the recommendation exactly?

[rodabod]

I usually judge the remaining lifespan of cleaning fluids (and rinse) by colour. And in some circumstances of they leave any residue. Water-based cleaners can become saturated with an oil emulsion that leaves a film on items. 
 

Regarding cleaning duration. It’s a tricky one. For my cheap ultrasonic, I don’t run it for longer than 5 minutes as that seems to kill them sooner. I’ve had four of them now. If I were doing watch parts in them (which I don’t generally) then I’d soak at 50 degrees for maybe 5 minutes and then run an ultrasonic cycle for 5 minutes. I think mine is 50W - that will obviously have a bearing on how long you use it for. 

[JohnR725]

maybe do a search to the message board we've discussed this before see what other people are doing. I'm attaching some images give you some clues notice one of the cautions on the temperature the cleaning fluid? then I snipped out images of same technical sheet but of differing times the colored one is considerably newer than the one it's in black and white. So there's been some minor changes in timing. Also notice how hot you should heat up those solutions? Then the unfortunate problem Swiss company zero reference to L&R .

[nickelsilver]

All commercial watch cleaning solutions, in my opinion, are too aggressive. But I'm a weirdo who doesn't mind cleaning twice and pegging jewels and so forth.

I use, what's in my opinion, the mildest watch cleaner, Greiner. Water based, not aggressive. A week ago I had a mainspring barrell that lost its plating. I know it wasn't due to my feeble Greiner soap. It was compromised by multiple cleanings in aggressive "high volume" cleaners. Yeah, it was probably poorly plated from day one. But I've seen enough early Omegas with their "copper" plating that's faded to brass to know.

Personally, pro watchmaker, I rather clean twice and peg and brush and keep the watch "intact" than deal with potential crap. With really antique pieces it's usually a piece by piece cleaning, like the old days.

But- most watches will stand up to the strongest cleaners 3,4,5 times in a row zero problem (even +6,7 etc times). But, some dont.

[rodabod]

NS, is that the red coloured Greiner soap, the 1:20 stuff? I use that, but I did once lose plating on a Buren Cal 462 which has a very thin plate when using it. If it’s the stuff I’m thinking of, it has added amines instead of ammonia which effectively makes it less aggressive (although obviously the concentration used affects this). 

[Kraai]

Galvanic corrosion is caused by self-induced current created by electrical potential
of two dissimilar metals in contact with an electrolyte. It can occur when two dissimilar metals 
(such as copper tube and steel pipe) are connected in the presence 
of an electrolyte.

Traces of water (in combination with ammonia) in the L&R liquid can make it conductive and thus can
cause this corrosion.

https://mb.nawcc.org/threads/l-r-cleaning-machine.27128/ :

L & R No. 3 for rinse. These solutions are NOT COMPATIBLE with water, even in microscopic amounts such as moist fingers. So if you use these solutions, don't get even the sightest TRACE of water anywhere near them or you'll ruin the solution. You won't know the solution is ruined until you examine the parts of a newly cleaned watch. There will be CRUD all over them which is TOUGH to get off.

 

[spectre6000]

Good point. The voltage range difference between brass alloys (-0.31V to -0.40V) and nickel (-0.9V to -0.2V) is between 0.11V and 0.2V. Cast iron and copper, for the classic relatable example, is as much as 0.42V. That's half the voltage potential, but still enough for some corrosion. The copper salts from the corroded brass of the previous movement make up the other part of that. Add any induced current from the ultrasonic inducers, and you've got yourself quite a cocktail...