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"Salt Spray Test on Clear Chem Film"



 

I recently went through my annual audit by one of the major aerospace primes and got "busted" for not running salt spray test on clear conversion coating (Mil-C-5541 [link is to free spec at Defense Logistics Agency, dla.mil]). I ran the panels and submitted them for test. First time around they passed with no problems (Panels came back super clean). Second time they failed (really bad). Does anyone have experience with clear conversion coating and salt spray testing?

Thomas Kristensen
- Arleta, California, USA
^


1st of two simultaneous responses--Mar  

I have ran a plating facility for the last 6 years and have found a number of problems that would contribute to a salt spray failure. First have you looked into the contaminate contents in your cleaning process, for example copper and chloride content in the deoxidizer. Another thing to look at is the chloride and sulfate content in the Alodine bath, they should not exceed 100 mg/l combined. Last but not least, are you monitoring the cleanliness of the rinse water? It is very important to monitor the TDS and meet the spec requirements. I run all my processes at the nominal times, temperatures, and concentrations to assure success.

Material could have an effect on the failure of panels, look to see if it was the same lot of material. We have also experienced the occasional lab problems and had no control to fix their process. Thanks and good luck

Steve Adams
- cedar city utah usa
^


2nd of two simultaneous responses-- Mar  

I would blame the quality of the panels that you used the second time, assuming that your process line is completely in specification. Old panels, made from aluminum sheet that has been around for a year or so is virtually guaranteed of failure. If it was sheared without flawlessly cleaning the shear bed, you can easily fail for red rust which you should never have on aluminum. Look at the panels very carefully before processing. I could point out areas that very nearly always pitted after the process and salt spray. Missed about half of the areas that did pit.

I have some doubts about several things. How many days or weeks later did you run the second set? How long has the line been in operation. What is the quality of the lab that did the salt spray. Did they do all of the checks or did they "pony" some of the daily data. While salt spray is a rather useless test, it is easy to operate the cabinet out of spec and have a high rate of failure.

James Watts
- Navarre, Florida
^


 

First, thanx for the reply's. It's appreciated.

It's only on my colorless coating where I have the problem. We use the same line for processing both clear and colored coatings with the exception of the chem film tank and there's no problem passing the monthly SS test with color coated panels. The panels are provided by the lab on a monthly basis and are thoroughly inspected prior to the coating process to ensure cleanliness. I've used the same lab for a couple of years without any problems and it seems like a reliable source. If they perform ALL the daily system checks and maintain their SS cabinets, I don't know, but I can see on the returned panels that they in fact have been exposed to SS. I'm thinking that maybe my chem film solution is the problem even though it's within specification parameters (analyzed weekly).

Thomas Kristensen
- Arleta, California
^

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