06:49 Jan-11-2010 carlo NDT Inspector aerospace, Canada, Joined Jan 2010 3
We prepare parts by etching(alkali etch) prior to penetrant inspection. We are currently experiencing indications coming out from our 2000 series aluminum parts. After doing the approved written procedure it bleeds back but when we look at it under white light and 10x magnification, I can hardly see any unacceptable discontinuity base on the specifications. Is this acceptable or not?
The indications are all over the surface of the parts under black light. Is there any suggestions or inputs with the significance and how to make proper evaluation? Is there any one who experienced the same thing as what we are experiencing?
We send out two sections of the part for metallurgical analysis. They examine the part by Stereomicroscopic examination, Fluorescent penetrant exam, Scanning Electron microscopy and Metallographic examination and found out that these "stars at night" type indications that we saw confirmed the presence of superficial surface indications and these are shallow etch pits. What is the effect of these indications on the part? The maximun depth was measured at 20 microns. The microstructure consisted of Aluminum alpha grains w/ a dispersion of non-metallic incluson(AlCu-FeMn) Thank you to your responses. I appreciate it really.
If not for metallurgical analysis we will not find out that it is etch pits. How can you evaluate this if you are inspecting it. They bleed back so tiny but all over the surface under black light but under magnifiaction 10x, you cannot distinguish these as pits or whatever, no metallurgical analysis yet, what would be your decision? who should be responsible in distinguishing these? Is it the NDT Inspector? I am just new in this career as level 2 and want to know who should be responsible. Me, I put them on-hold because i am not sure what it is. Is it the right thing to do? Any advise is highly appreciated. Thank you.
(We are anodizing these parts in-house)