Will pretreating chrome moly tubing with an iron phosphate acid cleaner at 150 F and a 4.5 pH for 10 seconds cause any heavy metals to be dissolved into the waste effluent?
It is all a matter of time. A single short exposure will not produce any measurable dissolved metals, but eventually over time, I would expect there to be some buildup of dissolved ions. There would be very low levels of dissolved metals including chromium, molybdenum and probably nickel (assuming the tubing you are talking about is austenitic stainless steel).
How low a level depends on the production volume (i.e., the total surface area processed) and the time between tank dumps. Whether or not the bath would require special treatment and/or disposal would be a function of the wastewater regulations in your area. If this represents a small percentage of your total operation, there may not be enough to be detectable. If this is a continuous, three-shift operation with six months between tank dumps, it may be another story.
I would suggest you find a good test laboratory in your area. Set up a regular test program with them the next time you charge your tank and then start a regular sampling program. Start processing the production, then sample the tank (maybe starting off every other week). Have them analyze for the metals that would be of concern (chromium, molybdenum, nickel and any others) and compare with your discharge requirements. You may want to adjust the sampling program to be more or less frequent based on how the results are coming back.