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topic 49057

Salt Spray Test after Hard Anodising

A discussion started in 2008 and continuing through 2020 so far.
Adding your Q. / A. or Comment will restore it to our busy Current Topics page

June 14, 2008

Q. Does anybody know what is the equivalent comparison between exposing a Hard Anodised Sample to a Salt Spray Test in a Lab as opposed to keeping the sample immersed in a 5% Aqueous Solution in Salt in house, or is there no comparison at all?!
I am informed that 24 hour in a salt bath equals 160 hours in a salt spray chamber.Is this correct?
I am keeping 6061-T6 Hard Anodised Sample as per MIL-A-8625,Type3,Class1 in Salt Bath for 51 hours as a n equivalent for 336 hours in Salt Spray as per the standard requirement.
Samples do come out spotless.

Ravi Rao
Hard Anodising Facility Owner-Mechanical Engineer - Belgaum, Karnataka, India


June 21, 2008

A. Check your requirements as, in general, hardcoat Type III coatings do not require salt spray testing! There is a statement in the specification that "unless otherwise specified Type III coatings will be unsealed." Obviously unsealed coatings wouldn't stand a chance of passing 336 hours of salt spray. Also, it's not surprising that 6061 will pass - try 2024 as the specification default for corrosion panels suggests. As for the correlation between hours of salt spray and hours of immersion in a salt bath, I've never seen a requirement or standard for salt bath immersion. I've worked with finishing standards for 30 years the last 15 with both ASTM B8 committee and SAE's Committee B which over sees AMS specifications. I can't see why a salt bath immersion would be more corrosive that an elevated temperature, oxygen laden salt spray test. The bottom line is that regardless of what persons respond here, you're bound to comply with the requirements of Mil-A-8625 [link is to free spec spec at Defense Logistics Agency, dla.mil] and it dictates 336 hours of ASTM B117 [affil. link to spec at Techstreet] salt spray.

milt stevenson jr.
Milt Stevenson, Jr.
Anoplate Corporation
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June 24, 2008

Q. Dear Milt,
Thanks for your comments! Our Customer's drawings specify Nickel Acetate sealing after Hard Anodising as per MIL-A-8625,Type 3, Class 1. Hence Amendment 1 to Rev.F, page 2-correction with footnote, is applicable to us,
"Type 3 coatings shall be tested for corrosion only when it is specified that the coating is sealed."
Min.5 specimens need to be Salt Spray tested every month and it is quite expensive. Besides, it takes at least 15 days to get a report from the Lab. If I am processing 40000 sq. in. of material every day, I do not have any indication of the product quality (other than thickness and visual) for 45 days! 18,00,000 sq. inches later, it would be too late! So far my Salt Sprays have come out OK (spotless) -- but I am paranoid. Salt Bath immersion idea was my only consolation (however misplaced(?!)) until you threw it out!
Any Suggestions? Will be grateful!
Ravi

Ravi Rao [returning]
- Belgaum, India



December 7, 2020 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear sir,
Kindly suggest to me what are the reasons for hard anodizing 2024 series failing salt spray test ... we are using 12*4*0.063 panels; length 12 cm, breath 4 cm, thickness 0.063. We are doing it by current method as per AMS2482 [affil. link to spec at Techstreet] E.

Yabez yabi
- Bangalore/Karnataka, India

----
Ed. note: AMS 2482 is "Hard Anodic Coating on Aluminum Alloys Polytetrafluoroethylene (PTFE)-Impregnated or Codeposited"


December 2020

A. Hi Yabez. Keep in mind the perennial complaint about salt spray testing of 2024: it tends to be more a test of the freshness & quality of your test panels than of your process :-)

So I'd start with a test of a brand new panel from a different supplier before you make any changes to your process.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


December 9, 2020

A. Ted is spot on with his comments. The panels have a great deal to do with pass or fail.

drew nosti
Drew Nosti, CEF
Anodize USA
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Ladson, South Carolina
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