Sorry Ted, all I have is opinions on this since it is not a common plating product. If it is not HARD, then a phosphoric acid based cleaner is not a problem. But, some soft metals get very hard in the weld area which is where stresses are the greatest on many parts. I have used Ospho and always washed it off rather than letting it dry or wiping it off. Your product is a cleaner and a poor man's phosphate coating which is similar to products that have been used by thousands of people for years with little attention to quality and thus results are varied.
Most people find that it does a good job.
Thanks for the thoughts. The metal is automotive steel, as stated, and the range of types of steels covers the types in a 60s Detroit product. Carbon steels of various types from low-carbon to spring steel. Seems like I recall 375F for 2 hours as useful. But NO processing should be done in a kitchen.