Electrical contact resistance testing in MIL-DTL-5541

robanbieber

Involved In Discussions
#1
Trying to interpret MIL-DTL-5541F in regards to whether electrical resistance testing is a requirement or not to be done on our class 3 panels every month. According to table 1 that lists the process control tests the electrical contact resistance states a requirement paragraph of section 3.7. Section 3.7 states that for class 3 coatings "Electrical contact resistance testing shall be as specified in the contract or order (see 6.4). The test method, frequency of testing, and required resistance value shall be specified by the acquisition activity to meet the needs of a particular application (see 6.1.2.1)."
Well 6.4 states "Acquisition requirements. Acquisition documents should specify the following:"
...
h. If electrical resistance testing if required for class 3 coatings (see3.7 and 6.1.2).
i. When electrical resistance testing is required, specify the required resistance values, frequency of testing, and test method (see3.7 and 6.1.2)."

Well if I am reading that correctly unless the drawing specifically calls out the Mil spec AND electrical resistance testing is required OR the contract with the customer specifically calls out electrical resistance testing is required ON Class 3 test panels for chem converted parts used in their product then our company is not required to perform electrical resistance testing on the class 3 test panels that are going out for salt spray testing. Am I interpreting the mil-dtl-5541 document correctly? Thanks. And yes we are NADCAP certificated for the chem conversion process and we have been doing electrical resistance testing on our class 3 panels that we send out for salt spray testing every month.... just concerned that we are doing more work than what the requirements are... :frust:
 

Mike S.

An Early 'Cover'
#2
I have no expertise in coating, but it sounds like your interpretation is correct.

However, it is no sin to do more than required if you get some value from it. The requirements are minimums.

Only you know, or can determine, if that is the case or not. Does the resistance testing give you actionable data? Does the historical data show your process is in control? Does it help you verify your process is in control? Maybe by doing a resistance test it can save you doing more expensive tests elsewhere?
 

robanbieber

Involved In Discussions
#3
The problem is that the test is so damn sensitive. Coating the 6061 panel to Class 3 is no problem to pass salt spray but the electrical probe on our test fixture usually damages the coating and causes a failure. We know it is the probe that is damaging the coating because the pits occur in a repetitive pattern in the 10 areas that we press the probe into the panel to make the measurements. We wet sand the 1 inch square probe surface as smooth and flat as we can on a surface plate and take pains to ensure that the probe is contacting the base as flat as possible but usually to no avail. Just really frustrated having to explain that type of failure and if we do not have to do the test then it would remove that burden. :frust:
 

Mike S.

An Early 'Cover'
#4
I would think it relatively easy to explain that type of "failure" if the explanation were included in your documentation (procedure/work instruction, etc.).

Maybe add a small diagram or picture of a panel, showing where the resistance contacts are made, and stating that pitting there is not to be considered a failure and explain why.
 
Top