Is this wustite or something else?

[Lewis Downey]

Ok here is a cleaning question not about CI that is of little interest as a collectible. The piece is a Tabasco Sauce branded skillet.

1st picture
Before cleaning it was rusty with little visible seasoning. After a soak in the LB for a couple of days I scrubbed it and sent it of to the molasses bath.  Lately one of my cleaning strategies has been to think of the electro as final or near-final processing and to let the MB handle the bulk of rust removal on heavily rusted pieces. That is a change in strategy for me, previously I tossed a rusted piece into the electro for a short period of time and then threw it in the MB, and probably back into the electro afterwards.

2nd picture
After a few days in a 10% molasses bath followed by a scrub, it looked like the second picture. It was more or less gray iron with a few dark spots of unresolved rust. In my experience the electro is more effective at removing those dark spots than the MB.

This next part is iffy. It was late, and I don't trust my memory. Since there was rust remaining, I might have scrubbed the skillet with BKF but do not remember doing so.

I definitely scrubbed it with dawn and dried it as thoroughly as I could. It was set it on top of the stack of pieces waiting for the electro.  Lately my thinking is to build up a queue of pieces for the electro and not to worry about rust that builds up on the dry iron while it is in queue. Taking this approach has improved my skills at drying pieces, which in turn has helped reduce flash rust. Any new rust  that does occur is handled by the electro.

3rd picture
Lunchtime today I had a look at it and the surface was partially covered with a blue or blue gray rust-like substance.  And at long last, that is the essence of my question. What is that stuff? Wustite maybe? Whatever it is why did it form?

For reference the list below is from a comment in another thread.

...
Iron oxide is iron + oxygen.  The iron exists can exist in the ferrous (Fe++) and ferric (Fe+++) oxidation states:

*  Fe2O3 is hematite.  It is ferric iron.  It is orange-red.
*  Fe3O4 is magnetite.  It has two ferric and one ferrous iron.  It is black
*  FeO is wustite.  It is a non-stoichiometric mixture of 85 - 95 Fe atoms per 100 O atoms.  It is grey.
*  FeO(OH) is iron oxide-hydroxide.  It is ferric iron.  Its color ranges from yellow to brown.

Whatever the blue-gray stuff is, it seems to have been removed after a short stint in the electro and a scrub.