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Testing Iron Concentration in AMS 2700 Passivation Tank

hi, I work in the QA department, we are a coating factory that does chem film, anodizing, and passivation.

my question is:

AMS2700 para 3.1.2.2 : "iron concentration in the passivation bath shall not exceed 0.5 weight percent".

1. I want to define the frequency of the test, what do I have to do?

Roei Shabtay
employee - Barkan, Israel
February 22, 2010

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First of two simultaneous responses --

AMS2700 suggests using ARP 4992 as a guide for frequency of testing. In essence, it says to set a "process control limit" of 0 to .375%, and then start testing at a frequency that seems right to you. Do you do a lot of parts? Only a few? Once you set your frequency, measure the iron content per that frequency. Are three or more of any consecutive ten out of the process control range? If so, increase the frequency. If you get 10 consecutive readings within the process control limit, then decrease the frequency.

It might be worth getting a copy of ARP4992, so that when your customers ask why you do what you do, you can point to it to justify your procedures.

Lee Gearhart
metallurgist - E. Aurora, New York
February 24, 2010

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Second of two simultaneous responses -- February 25, 2010

Roei,

Determining your analysis frequency relies on previous analysis results.

If you have carried out this analysis historically then have a look at your rate of iron build up and determine an analysis frequency that means you can control within shop control limits and if exceeded the level of iron will not exceed the specification limits.

If you haven't got any history then you need to start the analysis. Start with a sensible frequency of analysis, for argument's sake, let's say it is guessed to be weekly. You should monitor your results and adjust your frequency accordingly. SAE-ARP 4992 is a good guidance document on determining your analysis frequency and also guides you when you need to increase or decrease your analysis frequency.

Brian Terry
Aerospace - Yeovil, Somerset, UK