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topic 18197

Alocrom / Alodine 1200 Salt Spray Tests


2002

Q. I am having problems with intermittent salt spray test results on 2024-T3 test panels in accordance with AMS C5541 [withdrawn / link is to spec at TechStreet].

The results over the past few months are as follows, fail / pass / fail / pass / pass / pass / fail.

If the solution records, titration's, ph, temp etc are examined there is no discernible pattern to the failures with regard to these factors. The Alocrom bath would seem to be running within the required parameters. I have also checked the rest of the line and again things seem to be running normally.

However, during my investigations I treated another set of panels and observed 'fizzing' whilst the panels were immersed in the Alocrom solution. Clouds of tiny bubbles forming continuously over the entire surface of the panels and rising to the surface. This is something I have not come across before. I repeated the treatment process with a 6082 panel and the 'fizzing' did not occur.

Does anyone have any ideas ? Is this an indication that there is a problem with the panels rather than the treatment line ?

The last set of failed panels showed 2 panels clear of any corrosion 1 panel with 3 corrosion spots and the remaining 2 panels failed drastically with greater than 15 spots each.

Thanks in advance for any info.

Rich Mosley
- UK


2002

A. Hi Rich,

The variance in results may be due to the salt spray cabinet itself. The salt spray test is notorious for its poor reproducibility. Thus, it is essential to run controls for comparison purposes. I would suggest that lab-prepared panels using your process would be a good start. If the lab panels pass and the production panels fail, you can investigate your line further to find the cause of the problem. If the production panels give the same result as the lab panels and both pass, everything is OK. If they both fail, then something funny is happening in your salt spray cabinet.

George Gorecki
- Naperville, Illinois


2002

A. Seems you are border line on the fence. Look at the panels very carefully under 10X loop, scratch a circle around each pit, then see if that is where the failures are occurring. Do not heat to dry. Leave in air for 24 hours. The single most frequent problem with salt failures rest with the starting aluminum panel.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como
and co-author of The Sulfamate Nickel How-To Guide



September 11, 2013

Q. Hello,

I have a quick question.

A cast aluminium part is coated with clear Chromate Conversion Coating.
We have run a 24-hour salt spray test, and the surface color has turned to a dark grey. Is this normal?

18197

There are no signs of white oxidation or corrosion, other than a few salt deposits left after the test. Many thanks.

Russ H
- UK


September 12, 2013

A. Color change is normal and acceptable: most MIL and BAC specs even state :"Loss of color shall not be cause for rejection". The color change is due to the heat and humidity of the extreme environment within the chamber.

Fauna Tester
- Seattle, Washington USA



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