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"Need harder nickel-free plating for zipper sliders"

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January 28, 2020

Q. Hi All,
Love the forum and all your work!
I make leather accessories, and source hardware from China and Italy and Japan.
This enquiry relates to our zipper sliders which are the little carriage that combines and separates the zipper teeth.

"Zipper: An Exploration in Novelty"
by Robert D. Friedel
from Abe Books

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They are die cast from zinc, and then electroplated to our desired colours.
Those colours being rose gold (I assume bright acid copper) with a lacquer, a gold colour (Not a straight brass, but I'm not sure of what colour) and a silver colour that is called nickel-free.
Over the last couple of years with our current supplier, we have found zippers that are opening behind the slider as the zipper is pulled closed.
The obvious culprit would be teeth wear, but this is not the case. While the teeth do wear over time, it is always the slider that has worn on the internal surfaces and is no longer combining the teeth correctly. (*On a 10+ year old zipper it might be the teeth, but the slider would have likely gone first)
We are seeing this in as little as 6 months in high use items with 20 odd openings/closings per day.
We make our items to last, and ideally want a minimum life of 3-5 years, so a slider failure after 6 months is a disaster from a reputation standpoint.
(We don't claim 3-5 years and only offer a 12 month warranty, but we fix anyone's bags for free for life basically [within reason]).
So when anyone presents with this fault, we replace the slider and problem is (temporarily) fixed.
Problem is, We sell to tourists and many of those will not be able to come back, and if they have the problem, they may just assume our product is not good and write us off.
Our old suppliers slider did not have this problem, and I still occasionally see them at 10 years old and going strong.
I have asked our current supplier about why, and they have no idea ... initially I thought changing sliders would solve the problem. As it must have been something about the internal geometry that was different, and causing the problem, but in the middle of the night I was lying there thinking about it, and it occurred to me, that the thin plating they put on the current sliders has very little abrasive resistance, and the same would likely be true of the inside.
In basic tests I have tried previously, the current pullers (the tab attached to the slider) which are plated while attached to the slider, in as little as 6 short pulls across a green scotch brite pad, it would already be worn through the silver colour, to the copper underneath, and quickly through that and to the zinc... the old puller could go more than 40 pulls of the same nature and not get through the silver.
So ... cutting an extremely long story short, I think this lack of thickness, and possibly hardness, is the reason for the premature failure of the sliders.
Now to my question!
I want to get my supplier to get some sort of harder and thicker plating down on the initial raw/polished slider, before it is sent to the decorative plater.
I should have mentioned before that they are rack plated, not barrel.
So my question is, what sort of hard coating would be ideal? Nickel? And if yes, what thickness would provide some good wear resistance, and still be achievable for these kind of low cost items?
I know there are lots of ways to get a hard finish, but I need a simple affordable solution. I don't have contacts over there who can manage this issue unfortunately, and my contact would be one of the the only ones who can speak english in the company. He also knows nothing about electroplating.
Getting them plated here is not an option unfortunately either.
To give you an idea, the slider and puller combined are a USD$.05 item, and the highly polished rack plating with lacquer takes that cost to about USD $0.30 in total, plus the zipper and assembly etc. I understand that this extra process will cost more, and happy to pay to improve our product, but it definitely can't increase the cost by $1, as our margins would not allow that.
I think the hard base plate would solve our issues, and be achievable for those platers, or another plater in the region, but I lack the technical knowledge to ask for what I need or source another supplier, so any advice anyone can offer would be greatly appreciated.
Thanks in advance,
Ben :)
Btw, old suppliers zippers were not up to scratch and they would not give me the details of just their electroplater.

Ben Thompson
Owner/ maker /product source - Sydney, NSW Australia

"Nickel Allergy"
from Abe Books

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January 2020

A. Hi Ben. I think there is a little misunderstanding here which should be sorted out before we proceed. "Nickel-free" is not a color, it means that there is no nickel in the part (some people get a skin rash from contact with nickel). So if you solve the problem by nickel plating you cannot call it "nickel-free".

I'm not sure why you must do rack plating, which probably does not offer as good plating on the internal areas as barrel plating would.

You could be right that your nickel-free plating is not hard enough and that a harder nickel-free plating material is available, but I'm not personally familiar with the practicalities of such; you could certainly have chrome plating done, which is an exceptionally hard metal (but it would be hard to put other decorative plating on top of it).

To me the more promising possibilities while remaining nickel-free are thicker plating or harder die castings.

Regarding logistics, you decry the communication difficulties with China, while feeling Australian costs are too high. Have you considered the cost of manufacture in English-speaking India?


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

January 30, 2020

Q. Hi Ted,

Thanks so much for replying.

I was possibly not clear about the "Nickel free" finish. The Term nickel free is used by a few suppliers I have dealt with as the name for the silver colour.

I am aware it is not a colour, and is just a term for nickel free plating, but that's not how they use it, and for brevity, I probably glossed over that bit.

"Nickel and the Skin"
from Abe Books

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I do not require these items to be nickel free, as they are not in direct contact with the skin (and we don't sell anywhere in Europe), so I thought that the actual nickel plating would likely be harder than whatever silverish alloy they call "nickel free", and probably a simple solution, as finding a plater to plate nickel might be easier than the r & d of trying to get a chrome base to work.

My understanding of why we rack plate is that we require a highly polished finish on a small item with tight angles, and barrel plating will not give the desired results as polishing stones can not get in to all the little crevices etc.

Changing to another zipper supplier is unfortunately not an option, as it took me 10 years to find the current supplier, and I have not been able to find any others who can match their quality in terms of teeth, and finishing.

An Indian plater would be an option, but that would require shipping the sliders to India, and hopefully getting the desired result, then shipping them back to China for finishing and assembly.

I feel a much simpler option would be to get the existing plater to do the existing plating thicker or to put a thicker layer of actual nickel. Or to get them to find another plater nearby who can do what we need, so I want to be armed with the specific of what I need before asking again to improve the plating.

I should have mentioned previously, that we are talking about 5000-10,000 units per annum of a small component of a small (but important) part of our bags, and therefore this is not something that I could justify flying to china to take care of.

Also, I have previously asked them to increase the plating thickness, and they have said the only option is to run the parts through the whole process twice, as our plating run is way too small to be done on its own... It's put in with tens of thousands of others.

So, to cut an extremely long story short again, my question is; Is nickel plate likely much harder than most silver colour "nickel free" finishes used in decorative plating of small inexpensive items? (excluding Chrome of course).

And what sort of thickness should I be requesting? Would 5 or 50 microns of nickel be suitable, and would it be a reasonable request? And if Nickel is not harder than the alloy currently used, what thickness of that should I ask for.

I will definitely take your advice re the barrel plating, and see if that's an option for the slider its self, and maybe they can get the desired smooth finish.

... and I just read the title of my post and I know see why it looks like a wanted a nickel free plating option... face palm emoji.

Thanks again for your advice Ted,

Ben :)

Ben Thompson [returning]
- Sydney, NSW, Australia

February 3, 2020

A. Without knowing all the ins and outs of your relationship with your plater, I'll make a few comments:

It should be possible to barrel plate to good appearance and adequate thickness to prolong useful life, and it should cost less than rack plating.

You could also use electroless nickel applied in barrels or, possibly baskets. Properly done, electroless should have a good bright appearance, and is a bit harder than electroplated, possibly providing longer wear.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

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