I am using Mil-T-21014, Class 4 sintered tungsten (97% tungsten - 3% ferrous) for balance weights in what is suppose to be a nitrogen environment.  Integrity of the nitrogen environment was inadvertenly compromised through a design change.  Moderate corrosion like rust appeared on the balance weights during this period.  The condition allowing water into the environment has been corrected and is no longer an issue, but I am being asked to apply a conformal coating to the tungsten balance weights to prevent a re-occurrence.  I don't want to use anything that will add weight since balancing of this device is critical.  I would prefer to do nothing but management wants to do something even if it's not now necessary.  I would also prefer not to use a non-ferrous sintered tungsten (e.g. non-magnetic Class 3) because this would change my material density.  Any suggestions?