Ask the Expert Question-and-Answer Archive

by Ron Joseph

June, 2002

Robotic Tripping

Q. Our problem is paint with high aluminium contents (especially silver) cause a high voltage trip on the auto machine. What we are led to believe is that the aluminium forms a chain (due to the high concentration of aluminium) and shorts out between the application spray gun (REA) and the metal body being sprayed.

Have you ever heard of this phenomenon ?

Is there a difference between coated and uncoated aluminium ? And would coated aluminium circumvent this problem ?

I'm aware that the use a product or system called "voltage blocks" on waterborne paint, is there not something similar that we can use or solventborne products ?

What do you suggest we do to overcome this condition ?

Thanks

A. It is possible for metallic pigments to conduct the current that it picks up from the electrode on the REA gun or from the corona. Usually, electrostatic the charge goes back to the pressure pot, rather than to the grounded metal that you are painting. If the pressure pot is grounded, then the charge simply bleeds back to the ground and the system no longer functions.

If that is your problem, then I expect that the voltage block system used with waterborne paints can be used here as well. Alternatively, you might check with your paint supplier for non-conductive aluminum pigments. In any case, both your paint supplier and your Ransberg technical representative should be able to help you as this is a very common problem.

I will make some inquiries from this end for you, but it might take a week or so before I can get back to you.