I was degreasing a batch of small parts today in preparation for de-rusting. Acetone being expensive, i bath them in Varsol first (mineral spirits) and then spray them with Zep Heavy Duty Cleaner (neat) leave them for ten or so minutes and then add hot water to submerge them completely.
At this last step something interesting happens chemically, as the whole pot seems to be simmering. There seems to be no heat generated (as far as I can tell given the hot water) but there is a continuous swirl and bubble generation. I cannot smell any gas I can recognize (but the room is already permeated by the smell of Varsol). The water turns brown.
I am puzzled as to the nature of the chemical reaction occuring. It goes on for about 20 minutes or more. My thoughts were:
1) Zep and residual Varsol - but there is only little Varsol left clinging on the parts. The reaction should be over sooner.
2) Zep and metal - steel and zinc in this case - but there is no obvious evidence of surface etching (as there is e.g. if I put the same parts into ferric chloride for a short period. Plus there is no similar apperance of a reaction with FeCl).
3) Zep and rust - but why?
4) Something completely different or more complex.
I am not particularly concerned at this stage, just wondering if I hit onto something useful.
Any thoughts?