Ultrasonic examination of coated parts

A method for inspecting a coated material applied to a metal plate, the method comprising the steps of:

• directing a beam of ultrasonic energy through a coupling medium into a coating of the metal plate, the coating defining a surface wherein the beam propagates at a first velocity through the medium, and wherein the beam propagates at a second velocity in the coating, and wherein the coating surface defines a local normal, and wherein the beam is directed at a first angle measured from the local normal, wherein a second angle with respect to the local normal is defined as the arcsine of the first velocity of the beam through the coupling medium divided by the second velocity of the beam through the coating, and wherein a third angle is defined with respect to the local normal at which the beam is substantially reflected from the plate, and wherein an arc angle is defined between the second angle and the third angle, wherein the first angle is about the second angle plus fifty percent of the arc angle;
• and
• receiving with a transducer a reflected signal from the beam indicative of material discontinuities or delaminations or disbonds within the coating.

A method of inspecting a coating of metal object having a coating surface comprising the steps of:

• directing a beam of ultrasonic energy through a coupling medium into the coating at a first angle from a line normal to the coating so that a portion of the ultrasonic energy penetrates along the surface of the coating and a portion of the ultrasonic energy penetrates opposite the line normal to the coating and wherein the energy penetrating opposite the line normal to the coating is polarized;
• detecting energy reflected from the portion of the energy propagating along the surface to detect the surface roughness of the object, and
• detecting energy reflected from the portion penetrating opposite the line normal to the coating to detect material discontinuities or delaminations or disbonds in the coating.