NDT Inspection Method Applicability

Metal etch methods, both chemical and anodic, are typically used to detect grain structure, grain segregation, cracks, micro-shrinkage, or other discontinuities that are open or otherwise connected to the surface of a part being inspected. In general, etching as an NDT method can be applied at any point during the manufacture and/or in-service use of an applicable part. Surface defects as small as .015" (.38mm) can be reliably detected with metal etch methods.

In aerospace applications for example, etching is commonly used on aluminum, carbon steel, stainless steel, nickel and titanium. 
  

Metal Etch Methods are applied
in a range of tanks and chemicals
in our Acid Room

We offer the following types of metal etching: Aluminum, Anodic, Macro, Nital, and Blue Etch Anodize (BEA). Anodic etch is applicable to both stainless steel and nickel. Macro (chemical) etch can be used on both nickel and titanium. Nital etch, a.k.a., Surface Temper, can be used on either carbon or stainless steels. BEA is limited to titanium. Please see our Metal Etching, Acid Room, and Blue Etch Anodize literature for additional details of this technology. 

Etch is used in the manufacturing process to remove scale, Alpha case from titanium, and to bring dimensions into tolerance. Metal etch can also be used to assist in Destructive Testing (DT). After a part is sectioned and polished, it is then etched to further expose grain size, flow, weld geometry, etc.