Brian:
I don't want to seem sharp, so I apologize if this kind of thing pushes me over the edge occasionally. But, within my admittedly limited knowledge of chemistry, there is no mechanism by which simple acids or ionic solutions are "activated" in any sense.
It seems that you're starting from the assumption that the item being plated is well drained, then trying to figure out some way that the damage could be occurring, and the mechanism you've come up with involves some chemistry that is highly questionable, at best. The question I have is, how do you KNOW that the item experiencing the damage really has been well drained? It seems like the simple explanation is that, once in a while, the item just doesn't get drained well, in spite of your providing good drainage holes. Even with extra holes, someone has to go to a lot of effort to get all the chemicals out of the inside. Even under the best circumstances, it takes a lot of care. There are lots of corners and potential gaps in any structure with tubes and several parts brazed to them. It's very difficult to force water into all the parts and to flush things out.
So, my suggested explanation for post-plating corrosion is something like this:
1. Guy in the plating shop is a tad hung over. (Lesson: don't do your replating on Monday mornings!)
2. The guy does not flush the tubes well. Just goes through a perfunctory cleaning.
3. Some chemicals and water are left in the tube. Some of this is in a gap(say, between tube and lug), where it does not dry quickly, allowing corrosion to occur. That same gap may have had residue from a previous plating. If that residue were dry, it would not have caused any corrosion. Now, however, because it's difficult to wash out into the plating solution, it might increase the concentration locally. This is the closest to some kind of "activation" that I can imagine.
4. New moisture, perhaps from condensation on cool mornings, prevents the solution in the crack from drying. So, corrosion continues.
This is a combination of random conditions--carelessness and weather--which would explain why it happens infrequently.
My suggestion as to how this occurs may or may not be right, but at least it is technically plausible. It is surprising how long it takes liquids--even very volatile ones--to evaporate from a partially closed container. A little leftover water, along with some chemical salts, seems quite enough to do some significant corrosion damage.
Again, I apologize if I get a little heated on some of these issues. Usually I just let them go by, but occasionally it's too much to ignore. Then I tend to overreact. I like dealing with the technical aspects of cycling, even though they are often pretty basic. Unfortunately, it tends to generate a lot of technical ideas that are just plain wrong. If you don't challenge these at the outset, they quickly become part of the conventional wisdom, and it's then pretty hard to dispel them.
Steve Maas Dublin, Ireland
brianbaylis@juno.com wrote:
> Steve,
>
> There are two issues. One, often original plating jobs were done with only one drain hole in an enclosed tube. This means that the original chemicals, even if only fresh water, is left inside the tubes in suffecient amount to possibly cause rust to begin inside. It seems to "reactivate" when put through a replating process; wheather it is simple rust or an actual acid rich mixture. Even brazing flux from the dropout attachment operation can supply corrosive content to any moisture trapped inside.
>
> Since actual rusting through of tubes is quite rare, and the examples I've seen have all been in areas where there was original chrome and then a rechrome; I am assumeing that the original plating and the new plating are both involved in the resulting damage, in the rare cases when this does happen. Also, both examples sat for a period of a few months after the restoration, and even before they were built up began to show signs of this problem comming from inside the tubes. If it were the recent plating, supplied to the plater with proper drainage, the rust could not possibly rust through in that short amount of time. Clearely the majority of the damage has taken place during the previous 30 or more years of the bike's life. The new plating is just what resets the action going again and it finishes the job that was started long ago. This is how it looks from what I've seen and experienced over a long period of time. There may be some other explaination. The good news is, a
ll this is still pretty rare.
>
> Second, the issue of contaminating plating tanks. My plater requires me to provide parts that have easy and complete drainage. The reasons are that of dragging chemicals from tank to tank, a plating no-no; and also of time savings. If the stuff drains quickly and easily they are much happier. Personally, I completely close my tubes as I finish up the brazing, so as to have NO holes if it goes to the plater; but for bikes that originally only have one hole, they must have 2 to be plated. So that way I'm sure there is nothing lest behind once we get done with it. I can't do anything about what happened before it came my way. That's the way the business is.
>
> Brian Baylis
> La mesa, CA
> A little bit of chrome is good, so more chrome must be....A pain in the ass.
>
> -- Steve Maas <stevem@mail.nonlintec.com> wrote:
> Brian:
>
> I lost part of this--your paragraphs are getting clipped at 1024
> characters, I think. Unfortunately, right where you cut to the chase.
> Not sure if it's at my end, yours, or just a 1024-character buffer
> somewhere out in cyberspace.
>
> In any case, I think you are describing simple contamination from
> inadequate flushing. How do you know that the contamination causing
> corrosion comes from the original plating, and is not left over from the
> second, replating operation? Seems to me that any chemicals (which are,
> after all, water soluble) left over from the original plating would
> dissolve in the replating, and be negligible relative to the amount in
> the new solution.
>
> Part of my problem here, I admit, is terminology. Acids are by
> definition water solutions containing excess hydrogen ions. They don't
> get "activated," although they can be created by dissolving substances
> that disassociate and liberate hydrogen ions. And, of course, acids
> aren't the world's only oxidizing agents, but that's a separate issue.
>
> Steve Maas
> Dublin, Ireland
>
>
> brianbaylis@juno.com wrote:
>
>
>>Steve,
>>
>>OK, let me explain how this can work. I've seen it a few times. It may be somewhat rare, but it does occur. There is no way to tell in advance what the bike has been going through in it's years previous to being replated, but here's the way it happens. Almost every Italian frame I've ever seen that has chrome on the forks or stays has only one heat release hole in the fork blade or stay (seat stay). When the part is originally chromed, when plating solutions enter the tubes, they are never completely flushed out and complete drainage is impossible with only one hole in the tube. So there is not neccessarily a large amount inside the tube and maybe only a small amount, but it is there and the acids can be activated with the introduction of any moisture. That's the beginning, the original plating job left some solution behind; not enough to eat through the tube at the time or even over time. BUT! When a bike is replated the first thing that happens is the part must be stripp
>
>
> ed of the old chrome. This is done by
>
>>Before anything goes to the plater I make sure each tube has two holes in it so all solutions can drain completely and the plater does not drag chemicals from one tank to another while doing the job. This insures that nothing new is left behind, but I've seen a few occassions where about 6 months to a year after the new plating the tubes begin to rust through from the inside. There is very little that can be done from there short of either some serious repair work or tube replacements. One can see or even predict in advance that this may occur. There is a certain amount of risk in doing a restoration that involves chrome plating. Rely on experts with lots of experience with chrome to have the best odds of success. All of the chrome related problems I've seen involve either a plater who doesn't know how to do bikes properly or a customer who has taken matters into their own hands and caused a problem in some way, with the few exceptions being the latent acids. Technically,
>
>
> that is from plater error also. I've
>
>>So, the word "nonsense" will only appear in my explaination in this sentence. It can happen, although rare. I hope this helps you understand how this can happen. Stripping old chrome, polishing steel, and replating old frames involves a fair amount of work and a lot of care. Each situation presents a challange unique to the part in question and the people who handle the work need to adapt to each case the best they can. Working with old parts, especially chrome parts that have become rusty, requires the ability to judge how to best do the job and where to draw the line before lugs or crowns get too thin. By far the most difficult typical part is the Masi sand cast Fischer fork crowns. They are very pitted deep into the casting and it's nearly impossible to remove some of the pits.
>>
>>Brian Baylis
>>La Mesa, CA
>>Whe do lots of chrome and it's generally a pain in the ass.
>>
>>
>>
>>-- Steve Maas <stevem@mail.nonlintec.com> wrote:
>>Here comes the resident evil-tempered curmudgeon and technological
>>bluestocking again with more grumpy skepticism.
>>
>>I recognize that my chemistry is not what it once was--but,
>>f'hevvinsake, precisely HOW does rechroming "chemically reactivate
>>acids"? With 1000+ list members, we should have a chemist or two among
>>us. Maybe even one who is a plating specialist. I'd like to hear from
>>one of them on this issue. (I suspect that the word "nonsense" will show
>>up in their replies.)
>>
>>The simple fact, however, is that things are replated all the
>>time--motorcycle parts, car parts, household items, and so on--and I've
>>never heard this kind of concern applied to them. Corrosion after
>>replating does happen, of course, but is caused by inadequate cleaning,
>>not some kind of "reactivation," whatever that might be.
>>
>>Steve Maas
>>Dublin, Ireland
>>
>>
>>Jonathan Cowden wrote:
>>
>>
>>
>>>This from Vintage Cycle Studios:
>>>
>>>"in some cases, redoing existing chrome may chemically reactivate left
>>>over acids used as part of the original chroming process. These acids
>>>may cause severe internal tube corrosion that may lead to rust- through
>>>areas."
>>>
>>>Best regards, Jonathan Cowden Carpinteria, Ca
>>>
>>>
>>>
>>>>Let me just comment that Waterford will not re-chrome. I learned this
>>>>when they were still Schwinn, when they repaired the frame on my
>>>>formerly all-chrome '65. Gave me my choice of colors and did a lovely
>>>>job, but not chrome.
>>>>
>>>>Last year, when I had the '38 repainted by Waterford, I believe I
>>>>noticed the same thing on the web site, or when I asked about redoing
>>>>what had been a chrome fork on that bike. Again, the answer was
>>>>negative.
>>>>
>>>>I suspect there is a reason...
>>>>
>>>>harvey sachs
>>>>mcLean va
>>>>
>>>>_______________________________________________
>>>>
>>>
>>>
>>>
>>>_______________________________________________
>>>
>>>.
>>>
>>
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