Blue etch (Titanium Alloy)

Blue Etch (blue attack) is an anodizing process performed in a bath of trisodium phosphate followed by a controlled pickling operation to remove the oxide layer formed during this phase of anodizing.


Scope of application

The purpose of the process is to highlight the structure and detect visible indications on the surface such as:

  • Chemical segregations, α, β and silicides
  • Inclusions
  • Porosity
  • Cracking, forge folds and folds
  • Areas of overheating and areas of localised under-heating
  • Incrustation and inclusions
  • Heterogeneities
  • Shearing and separation
  • Areas of localised α-case contamination and oxide skins
  • Cold working
  • Local overheating caused by polishing or burning caused by machining
  • Sudden change in fibre, grain size or grain not recrystallized
  • And any other that is detectable by this inspection process (machining or handling faults)

This instruction applies to titanium and titanium alloy parts in all states of machining or rough from the forge if our customer requests a Blue anodic attack or "Blue Etch".

This instruction can be supplemented by specific instructions on the inspection range specific to the exhibit after our customer’s agreement.

Reference systems

DMC 0326 /AMS 2642 (SAFRAN), P3TF25 S12 (GE Aviation) and EIM code 3 (Pratt & Whitney) specifications

Sectors concerned: Aerospace, Medical, energy, etc.

Environmental impact

This process is not affected by ELV, RoHS or REACH regulations.