Best NDT method to detect De bonding , micro pitting on the MRB
 

I was wondering if there is a NDT technique which can give us accurate predictions on the onset of de bonding and pitting corrosion on the spar of the metallic Main Rotor Blades.
Eurocopter some does not endorse the Ultrasonic Testing and maintains the Tap Test as the best method.
Though in UT technique, latest methods include Phased Array methods.