Mixing phosphoric acid into Chassis Saver Polyurethane paint to spray inside Chassis? Maybe

 UPDATE: I did do this experiment - it seemed to have worked a bit. thanks

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pdf link

  iron phosphate coatings are typically utilized to improve the
adhesion of subsequent layers of paint to the substrate [19].
The phosphating process forms a thin film that neutralizes the potential of the anodic sites on the
substrate and impedes the corrosion reaction [20]. Concurrently, the substrate is positively
charged, increasing the number of active bonding sites.
The phosphating process can involve many steps depending on the desired result. Phosphating
procedures may include surface activation prior to immersing in the phosphating solution, a
neutralizing rinse after the initial rinse, application of additional coatings or sealers after drying,
or other additional steps [14]. The simplest iron phosphating procedure is as follows

  phosphating
has been vital to the automotive industry to prevent the development of corrosion and improve
adhesion of vehicle body paint [22]. For over 50 years, phosphating has also been a critical
practice in metal processing, advancements in dentistry, and the appliance industry, among other
industries [23].
In addition to being a component of a phosphating solution, phosphoric acid can also be utilized
as an additive to polyurethane coatings to improve adhesion [24]. 

 In general, the use of phosphoric acid derivatives as additives did not result in an increase in adhesion values.