Fretting
Posted: 21 Sep 2011 21:22
Ok Guys and Gals...Listen up...Recently the company I work for has been experiencing a rash of units coming back from the field. We make avionic flight displays. When they come back some of the time we can find no fault in the system or intermittent faults. Many times we just re-seat the connectors and the units work. These units have been in the field from 3 to 5 years...sometimes less.
After a lot of trouble shooting and testing I was able to find the root cause of the problem was fretting in the tin plated connectors. For those of you who don't know what fretting is (or think you don't because you do...if you own a TR7) movement of the mating contacts of a connector. Actually sometimes very slight repeated movement of two materials that are in contact with each other. Better explanation here...http://en.wikipedia.org/wiki/Fretting
This fretting in the presents of oxygen promotes corrosion. Most automotive connector contacts are plated with Tin, thus tin oxide forms, tin oxide is non conductive. So besides the dissimilar metals corrosion you get at the ground points you get other corrosion in the connectors.
The most widely used prevention method for fretting/corrosion in our type of connectors is lubrication/anti-oxidant. Yes, that Vaseline type grease you find gumming up old connectors.
Ah, so you say you are using those fancy sealed connectors? They will protect my connections from your fretting and corrosion...Not so !
A few years ago tests were conducted on the F-16. It was found that even the sealed Mil-Spec. connectors suffered from moisture,fretting and corrosion, even on the GOLD PLATED connectors.
So what ever connectors you use you might consider using the automotive type dielectric grease they sell at your local auto parts store.This grease not only lubricates your connections reducing fretting but also prevents oxygen from getting to your contacts preventing oxidation from forming....
Maintained on Saturday…Drive on Fun-Day !!! 1976 FHC - 1980 DHC
After a lot of trouble shooting and testing I was able to find the root cause of the problem was fretting in the tin plated connectors. For those of you who don't know what fretting is (or think you don't because you do...if you own a TR7) movement of the mating contacts of a connector. Actually sometimes very slight repeated movement of two materials that are in contact with each other. Better explanation here...http://en.wikipedia.org/wiki/Fretting
This fretting in the presents of oxygen promotes corrosion. Most automotive connector contacts are plated with Tin, thus tin oxide forms, tin oxide is non conductive. So besides the dissimilar metals corrosion you get at the ground points you get other corrosion in the connectors.
The most widely used prevention method for fretting/corrosion in our type of connectors is lubrication/anti-oxidant. Yes, that Vaseline type grease you find gumming up old connectors.
Ah, so you say you are using those fancy sealed connectors? They will protect my connections from your fretting and corrosion...Not so !
A few years ago tests were conducted on the F-16. It was found that even the sealed Mil-Spec. connectors suffered from moisture,fretting and corrosion, even on the GOLD PLATED connectors.
So what ever connectors you use you might consider using the automotive type dielectric grease they sell at your local auto parts store.This grease not only lubricates your connections reducing fretting but also prevents oxygen from getting to your contacts preventing oxidation from forming....
Maintained on Saturday…Drive on Fun-Day !!! 1976 FHC - 1980 DHC
