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Salt Spray Headache - Aluminum Panels fail test

2007

Hi Everyone,

Well it appears to me that I'm not the only one that has been getting a headache from salt spray testing. I've read a lot about it in the archives, tried quite a few suggestions but still failing for three months. Started operation at the end of 2005,never had a problem till this april. Only failed by one pit too many on one panel in April but the problem has gotten a lot worse in May and June.
I'll start with my tanks: Oakite [Chemetall] Products (Class 3)
1-NST Cleaner 120 degrees
2-Rinse
3-34L de-oxidizer
4-Rinse
5-L25 conversion coating 78-85 degrees
6-Rinse
7-Rinse with FH3 135-145 degrees
8 Dry 120 degrees
We are following MIL-DTL-5541 [on DLA]F class 3, I have changed out all of my tanks and scrubbed. Bought all new chemicals for the change out. Made all new test panels (6061 T-6) but I am a little suspect if the sheet was already older than 6 months.
Is there a certain way of prepping the panels prior to cleaning. e.g. sanding.
The tanks look great and our product has a beautiful color.
I sent two sets out to different labs in June. The one set we DA sanded, I let them sit over night wrapped in bubble wrap. It failed. The other was put on our Timesaver Deburr machine and sent to a different lab, still waiting for the results.
I'm getting very frustrated as you can all imagine. Is there anyone out there with any hints.

Hope you can help,
Thanks,

Micheline Forth
Metal Finishing Company - Rincon, Georgia, USA

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First of two simultaneous responses -- 2007

We used to DA sand older panels with 280 grit and then 400 grit and had no problems. As the panels got much older, more pits showed up and we would junk the panels before failures.
I personally pre-inspected all panels and threw out any that showed any hint of a pit while wet or dry and with an oblique light.
Storing a panel in vinyl or PVC is begging for trouble!
Set your panels (in the racks)outside in full sun for a couple of hours. It sets the gel and will give you a better test.

James Watts
- Navarre, Florida

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Second of two simultaneous responses -- 2007

Micheline,
The smoother the surface the better. Polished is best. No sanding unless really fine, e.g., #1200 wet sandpaper.
A lower temperature drying may help. Let the samples cure on the racks in room temperature air for 24 hours before handling.
Bubble wrapping isn't good, either, except outside of paper.

Get help from Chemetall Oakite.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

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2007

Hi Everyone,

Thanks.
The panels I sent to the second lab passed and not just by a little bit.
What exactly does the bubble wrap do to the panels?
I appreciate the help, I have a lot of info now. Hope it never happens again. WISHFUL THINKING.

Sincerely,
Micheline

Micheline Forth
- Rincon, Georgia, USA

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2007

As much as possible, procedures for the successful panels should be used in production.

Plastic wrapping may adhere to the chem film, especially that not fully cured.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.