being that mt is evaluated to visual criteria for aws d1.1. i would think that a rejectable indication would hold powder. not to mention if it would most likely be seen first, seeing how it would need a visual inspection prior to ndt.
Wow, didn't know that. I guess ASTM E125 should strike porosity from table 1, ASME should remove it from Section V, AWS should remove it as well.
E709 defines an indication as 16.1.1 Relevant Indications--Relevant indications are produced by leakage fields which are the result of discontinuities.
If all of those groups will allow MT with proper procedure considerations to search for Porosity, I guess they are unaware of this definition. By your
statement the flux field doesn't escape.. I suggest writing your paper and sending it in if you've proof of that. you'll make a fortune.
The only thing I'll agree with you on is it's not suited for small pores. But the idea that you can't get a flux leakage field on all of them I'll not agree to.
It would not be allowed in any of the mentioned codes as an MT indication relys on a leakage field (as you stated, poles being set up) to create the indication to start with.