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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Reducing smallest trace of salt on the surface before coating
May 2, 2017
Q. Hello everybody,
I face a difficult salt problem in my company.
Some of our clients impose us to have a chloride sodium (NaCl) rate on the surfaces of our devices below 1,8 µg/cm2 (= 18 mg/m2).
We use the Bresle patch method to determine this rate.
As an indication, our tap water show a 600 mg/m2 salt rate.
After meticulously degreasing our devices, we still have a rate around 100 mg/m2.
We tried some industrial products to apply before coating but none of them met our expectations.
I am starting to believe that our only option is to wash our devices with ultra pure water (type III).
So here is my question : have any of you already faced this kind of problem?
Do you know what solution we have to remove even the most tiny trace of salt?
P.S.: We apply coatings on raw aluminium, steel, inox. All that with or without cataphoresis. And we are far from any source of salt.
Thanks in advance for any information ! =)
Process engineer - Paris, France
A. Sodium chloride is very soluble in water which is the best solvent to remove it.
The water must be ultra pure.
Degreasing by any method is useless and probably a source of sodium chloride.
You are trying to detect very small amounts of contaminant so the patches must be handled with great care. Contaminated patches are a common source of erroneous readings.
Geoff Smith
Hampshire, England
May 2, 2017
A. In general, ultra-pure water is not required, but a DI water rinse with a conductivity of <5 µS is usually sufficient to meet your specs.
Lyle KirmanConsultant - Cleveland Heights
May 3, 2017
Q. Thank you for your answers.
I hoped there was a cheaper method than washing everything with DI water.
Did anyone ever find a degreaser which can also get rid of salt?
And thank you Geoff for your advice about patches' contamination but, sadly, I found it out "in the field" ^^'
- Paris, France
May 4, 2017
A. Hi Ludovic. There are proprietary formulations which claim to remove salt. It would be interesting if you tried some and told us the result of your surface analysis after using it because we have numerous threads on the subject.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 2017
May 10, 2017
Q. Okay, I already bought a bottle of "Chlor*Rid" and tried it manually (without dilution and pressure). I had to rinse my samples with ultra pure water after that and the results were kind of random (between 12 and 70 mg/m2).
We consider degreasing with a process involving steam distilled or DI water, added with a degreaser and Chlor*Rid.
I'll tell you if it's working! However if you have any tips, I'd be glad to read them.
I just spent 1 hour seeking threads about salt removing on this forum and I just find the discussion going on since 1995 ^^ (https://www.finishing.com/00/71.shtml)
You still cannot compare the different products here?
If you know some other guys working on this I would love to speak with them. Or let me know if there is an ongoing thread here where people work on that.
And thanks for your answers =)
- Paris, France
Hi again. All threads here are ongoing, including those from 1995; but we started a new thread for you rather than appending your inquiry to another because no applicable ones were really active.
People naturally want services exactly tailored to their desires of the moment, but is isn't always possible. This is very deliberately a "no registration required" site which is very unusual today and very good for a number of reasons, but thousands of postings over 22 years have proven absolutely & repeatedly that testimonials & comparisons of name brands simply don't work on this "no registration required" site. For example, we've received numerous testimonials offered under fictitious customer names where the IP address of the "satisfied customer" was the IP address of the product's website :-)
If you were the sales manager for a product, could you let stand a recommendation for a competitive product without posting paragraphs of spam (as happened here repeatedly), and without posting fictitiously (as happened here repeatedly), and without threatening legal action (as happened here repeatedly)?
Ideas like "Android is great but Apple sucks", or "Chevy Trucks are fabulous but Ford & Ram trucks are crap", or "Salt Remover X is much better than Salt Remover Y" are 99.9% worthless fanboy stuff anyway, so we don't post such claims :-(
If a supplier wants to advertise here, that's what has always paid for the media. But advertisements disguised as technical responses, or as testimonials from fictitious "satisfied customers", no thanks.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Okay, so after some tests I can say that steam washing did not reduce the salt contamination, either with or without an additive.
Notice that I used "dry" saturated steam.
- Paris, France
October 2, 2017
A. Hi. I don't think vapor degreasing will work; but if you want to leave no stone unturned ...
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2017
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