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Does ammonia wreck 14k?


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11 replies to this topic

#1 Tweel

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Posted 23 May 2007 - 09:42

I regularly use ammonia to clean pens, but some food for thought (or just worry...):

On the "Lion and Pen", in their repair forum, David Nishimura began a thread concerning the possibility that ammonia might cause stress corrosion cracking in 14k gold alloys. That thread has been idle since February, but some (admittedly unrigorous) Googling on my part seems to add support to the idea. The problem, if it's real, seems to be caused by the copper commonly used in these alloys.

Does anyone know more?

-- Brian

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#2 Oxonian

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Posted 23 May 2007 - 10:44

Hi Brian,

If the ammonia is at a high concentration and if you leave the 14ct gold nib in for a long time it might perhaps react with some of the copper on the surface and dissolve it out of an alloy and cause a few problems over time but in my opinion, (for what its worth and based on observation), if you use the low concentrations as usually mentioned (about 10% retail strength ammonia with water and remember the ammonia usually sold over the counter isn't 100% neat) and reasonable time periods, (hours rather than weeks,) I can't foresee any real problems with a decent 14ct nib and 10% ammonia solution.
Remember that not all that glisters is gold nor is everything that claims to be 14ct is solid 14ct, I have seen a couple of 'Warranted 14ct' nibs, with no mention of their being plated or filled, lose a 'laminate' from the surface, not from ammonia soak but just from age and use.

cheers, John



#3 Johnny Appleseed

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Posted 23 May 2007 - 15:12

David's post on Lion and Pen was mostly a call for research. He posed the question based on information from hourologists that ammonia can cause or contribute too stress crack corrosion in brass parts. There is very little research out there on the long term effects of different substances like ammonia on the very thin, highly distressed sheets of gold alloy that are used for nibs, so there is not a lot of information on it. David was fishing for someone with a mettalurgy background to look into this, or help look into this.

So to answer the question posed in the title of the thread, we don't know. Ammonia is used frequently to clean pens and many, many nibs have been soaked in ammonia and they neither dissolved nor cracked in half. The question David asked was more from the point of view of a collector and conservator of vintage pens, particularly very old vintage pens, and the standards of what consitutes "damage" is higher than it might be with modern pens or users.

Nibs, ammonia, and stress corrosion cracking, Is this a problem? - at Lion and Pen

John


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You should get a Yink, I think.

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#4 Tweel

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Posted 04 June 2009 - 01:53

Just thought I'd bump this up, as I came across a paper that seems to bear on this question. The article is:

"The Deterioration of Gold Alloys and Some Aspects of Their Conservation"
by David A. Scott
in Studies in Conservation, Vol. 28, No. 4 (Nov., 1983), pp. 194-203
Published by: International Institute for Conservation of Historic and Artistic Works

The following paragraph in particular caught my attention, in section 2.3, "Stress-corrosion cracking and embrittlement":

"A great deal of work has been carried out on the stress corrosion of gold-copper and gold-silver alloys, notably by Graf [27], Pickering [28] and Forty [29]. The behaviour of the alloys has been studied in aqueous solutions of ammonia, 2% ferric chloride, aqua regia, nitric acid, mercury, 10% potassium cyanide, and a number of other reagents. Even with the addition of a few percent of gold or silver, the alloys become susceptible to stress corrosion cracking. On the other hand, small additions of silver or copper to gold were not found to give rise to stress corrosion [27]. With further additions of gold to copper the susceptibility to stress corrosion increases until a maximum is reached, which is dependent on the nature of the aqueous environment. In general, alloys with from 10 to 30 atomic % are highly vulnerable (corresponding to about 25wt. % gold - 60wt. % gold for gold-copper alloys). The severity of the stress corrosion cracking then decreases as the gold content rises and should cease altogether once the gold content exceeds 40 atomic %. This corresponds to about 70wt.% gold for gold-copper alloys."

I'll give the citations below, in case anyone wants to know them.

In any case, it looks as though 14k gold is "highly vulnerable" to stress corrosion cracking due to exposure to ammonia, while the effect "should cease altogether" in 18k gold.

-- Brian

27 GRAF, L., and BUDKE, J., 'Zum Problem der Spannungskorrosion homogener Mischkristalle III: Abhangigkeit der Spannungskorrosionsempfindlichkeit von Kupfer-Gold und Silber-Gold Mischkristallen von Goldgehalt und Zusammenhang mit dem "Mischkristall-Effect"', Zeitschrift far Metallkunde 46 (1955) 378-385.

28 PICKERING, H. W., and WAGNER, C., 'Electrolytic dissolution of binary alloys containing a noble metal' Journal of the Electrochemical Society 114 (1967) 698-706.

29 FORTY, A. J., and ROWLANDS, G., 'A possible model for corrosion pitting and tunnelling in noble-metal alloys', Philosophical Magazine 43 (1981) 171-188.

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#5 Vintagepens

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Posted 04 June 2009 - 14:13

Thanks for the post.
We all may need to rethink our willingness to use ammonia on 14K nibs.

#6 PJohnP

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Posted 04 June 2009 - 14:34

An "aqueous ammonia" solution can be strong or weak, and the concentration would have a fairly significant effect on developing stress corrosion cracking. If one looks at the other solutions proposed, for example, 10% potassium cyanide, these are highly aggressive solutions with respect to corrosion. With that in mind, it's likely that some of the tests were done with a saturated ammonia solution in water, something quite different than the ones used by people cleaning pens.

As well, one needs to consider that corrosion effects are time based for exposure to corrosive materials. Stress corrosion effects are certainly not immediate, and do not typically occur for weak solution exposures on first contact. Prolonged exposure with weaker solutions can be an issue, but by prolonged, one needs consider that period as being significantly longer than a few moments in a flushing exercise.

Gold alloys are typically less susceptible to corrosion attacks than other metals, which is exactly why these are used in pen nibs. Inferior gold alloys, poorly plated nibs, mechanical metal flaws in fabrication could all allow for enhanced corrosion effects, but then, this is no different than for any metal use. Metallurgists considering corrosion effects are typically considering medium to long-term exposures of materials to corrosive agents. Their technical papers do not usually address transient exposures.

Is it appropriate to have measured concern about the use of dilute ammonia for cleaning pen components ? Yes, but with the proviso that the gold components are probably the least easily affected by ammonia. The prudent course of action would be to use dilute ammonia solutions for minimal periods, and to appropriately flush the pen of the ammonia solution. The need for careful handling of any cleaner, detergent solution, or other material in fountain pens cannot be underestimated, and ammonia is no different. Soaking a nib structure for many days or weeks in a strong ammonia solution would not be a well considered exercise.




John P.

#7 Ondina

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Posted 04 June 2009 - 14:46

Thank you so much, Tweel, this is an extremely useful information. As Mr. Nishimura states, a matter of reflexion as well.

#8 publius

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Posted 04 June 2009 - 15:32

It is necessary to observe that the term "stress corrosion cracking" indicates the presence of two factors. A fountain-pen nib, especially a flex nib, can be under significant loads in use, but presumably one would wash the ammonia out while writing. Some nibs are loaded to hold them between the feed & the section, & it is these which would be susceptible to stress-corrosion effects. Triumph nibs & others which are not so loaded should be much less susceptible.
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#9 rhr

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Posted 05 June 2009 - 01:40

You might also look at the patent cited in this thread on L&P, Topic 1225, for the effects of sulphur on gold nibs.

George Kovalenko.

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Edited by rhr, 05 June 2009 - 01:41.

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#10 Tweel

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Posted 05 June 2009 - 08:02

QUOTE (Vintagepens @ Jun 4 2009, 10:13 AM) <{POST_SNAPBACK}>
Thanks for the post.
We all may need to rethink our willingness to use ammonia on 14K nibs.

QUOTE (Ondina @ Jun 4 2009, 10:46 AM) <{POST_SNAPBACK}>
Thank you so much, Tweel, this is an extremely useful information. As Mr. Nishimura states, a matter of reflexion as well.

Thank you, guys -- I hope it's useful info, and not just alarmist static.

QUOTE (PJohnP @ Jun 4 2009, 10:34 AM) <{POST_SNAPBACK}>
Is it appropriate to have measured concern about the use of dilute ammonia for cleaning pen components ? Yes, but...

That's my feeling, too -- and possibly that using ammonia habitually on any given individual part (a nib, usually) might not be a good idea, at least for non-18k gold. I'm assuming (maybe wrongly?) that the cumulative effect of repeated exposures to weak solutions could eventually be as bad as a protracted single exposure to a strong solution.

QUOTE (publius @ Jun 4 2009, 11:32 AM) <{POST_SNAPBACK}>
It is necessary to observe that the term "stress corrosion cracking" indicates the presence of two factors. A fountain-pen nib, especially a flex nib, can be under significant loads in use...

The stresses that the article addresses are actually internal ones from working the gold alloy, though.

QUOTE (rhr @ Jun 4 2009, 09:40 PM) <{POST_SNAPBACK}>
You might also look at the patent cited in this thread on L&P, Topic 1225, for the effects of sulphur on gold nibs.

By coincidence, the paper I quoted also addresses sulphur compounds, particularly hydrogen sulphide, although they're identified as a source of surface corrosion (eventually eating down into the metal) rather than stress corrosion cracks. (It even refers to tumbaga and depletion gilding, as you mentioned on the Lion and Pen.)

***

I just hate it when the tail of an old, ink-corroded nib suddenly snaps, and don't want to cause the same experience for others in the future, in this case with an expedient cleaner that might be corrosive!

-- Brian

fpn_1375035941__postcard_swap.png * * * "Don't neglect to write me several times from different places when you may."
-- John Purdue (1863)


#11 PJohnP

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Posted 05 June 2009 - 17:42

QUOTE (Tweel @ Jun 5 2009, 02:02 AM) <{POST_SNAPBACK}>
That's my feeling, too -- and possibly that using ammonia habitually on any given individual part (a nib, usually) might not be a good idea, at least for non-18k gold. I'm assuming (maybe wrongly?) that the cumulative effect of repeated exposures to weak solutions could eventually be as bad as a protracted single exposure to a strong solution.


Brian :


I think for everyone who reads these articles/paper that it's necessary to understand that corrosivity discussions for industry or laboratory tests are a far cry from the occasional cleaning of fountain pens.

The industrial applications of corrosion chemistry and metallurgy are deep and wide both, but these applications addressed far far longer exposures and intensity of solutions than we see in typical FP cleaning and repair. Yes, stress corrosion cracking is a known phenomenon, and yes, pen nibs can crack, but the factors that are at play here are going to larger and different than using a dilute ammonia solution once or twice a year for most people.

In terms of the effects of repeated short term exposures having the same effects as long term exposures, no, that's not an equivalent condition. Long term exposure allows the ions that are attacking the base metal to migrate further into the crystal structure, developing additional corrosion effects, which then can have further effects if the metal is stressed /flexed while exposed to the solution. That's not to say that repeated exposures can't have effects, but that these would be different in how they manifest.

Now, should someone soak their pen overnight, once or twice a week, in a dilute ammonia solution, or if they daily, sluice the pen with a dilute or strong solution, well, heck, yes, there might be effects on the nib.

But as I mentioned earlier in the thread, I'd be more concerned about the effects of the dilute ammonia on other components than a nominal 14kt nib structure, and I'd comment that the use of any cleaner, solution, or non-ink material in a fountain pen should be short term in nature and the pen well flushed/cleaned with fresh water following the exposure. The much more likely case for nib cracking and failure is a manufacturing defect, perhaps subtle, in the formation of the nib where micro-fissures or cracks are present, and propagate either by creep or lateral cracking phenomena - these are the far common failure mechanisms. As physicians are wont to say in diagnosis, "If you you hear hoofbeats, don't assume zebras as the first cause on a working farm..."

If anyone's really keen on making some definitive determinations on this, I'd suggest taking a nib/feed assembly and soaking it in full strength household ammonia solution for say, a week or two, and then running a few quick tests on the strength of the assembly. I'll wager a figurative cyber-drink that the feed assembly and the nib restraint/holding mechanism will fail ahead of the nib cracking... hmm1.gif




John P.


#12 Ron Z

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Posted 05 June 2009 - 19:18

QUOTE
If anyone's really keen on making some definitive determinations on this, I'd suggest taking a nib/feed assembly and soaking it in full strength household ammonia solution for say, a week or two, and then running a few quick tests on the strength of the assembly. I'll wager a figurative cyber-drink that the feed assembly and the nib restraint/holding mechanism will fail ahead of the nib cracking... hmm1.gif
John P.


Good post.

Considering the fact that most of the exposure is short term, I don't consider the exposure to diluted ammonia to be a problem. In the shop, we're typically looking at one or two 3 minute cycles in an ultrasonic. For the average user, maybe one over night soak to get their pen clean.

I have had a couple of occasions where parts were soaked in straight ammonia for an extended period i.e. several days if not a full week. Granted, I didn't examine the nib under a microscope, but the nibs themselves were fine, with no cracks developing during the soak or later, no strength issues. It's the other parts that suffered.

I've seen a lot of cracks and other nib failures from people over flexing nibs etc., or from other stresses on the tail of the nib, but not from exposure to a cleaning solution containing ammonia.

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