As an emulsion.
https://en.wikipedia.org/wiki/Emulsion
The fact that Boric Oxide + water solution is immiscible is a good thing:
It means that the chemistry of the oil is not effected
while
making it easy to get the acid in contact with metal surfaces
where
It reacts with the metal to form the 0.5 micron thick layer of ceramic thats so hard and slippery.
In an engine:
Around 1 liter of water is produced for every liter of fuel burned:
HC + O2 = H2O + C (ideally)
So, thx to blowby, there is always an emulsion of water in the engine oil.
Said water is boiling off all the time when the engine is hot, making this easy for 2 reasons:
So you get the stronger acid in contact with surfaces easily where it forms the layer.
Any excess water is quickly boiled off.
Any excess powder lies in the sump where it slowly dissolves into produced water, replacing any ceramic layer that might manage to get scraped off.
(Additive manufacturers rely on this and only add 'nano' BO to to the oil with a "Shake Well".
The effect is very slow/gradual, vs the "WTF just happened!!?
" effect one gets after ~10km when adding the solution to an engine.
(Oil level needs to be topped up to full or almost so that the total mixture is not thinned out too much during that initial 10km))
Boiling off the excess Water in a differential and/or gearbox:
Not so easy, unless you get creative with a heat source. (Heat gun/s)
One can add a little oversaturated solution at a time until the desired result is attained an no further improvement noticed.|
Excess water will evaporate away slowly. (175 - 200 F helps here)
NB:
The Ceramic layer gets in under any sluge (from mixing different oil brands etc) causing it to collet in the sump and filter.
So replacing the filter only, once the B has 'kicked in' is a good idea.
NBB:
VW cars have a very fine sieve on the oil pump pickup which gets blocked by said sluge, causing low oil pressure, (tow in) and a sump removal and clean of it and the oil pickup sieve.
Not fun!