Phosphate Coating Heaters
The Teflon or PTFE immersion heaters are usually preferred to heat phosphate plating tanks.
By de-rating heaters, the wattage is reduced to 20 WSI, rather than the normal heat output of around
35-40 watts per square inch. You want to slow the crystalline buildup process on the heaters.

Phosphate conversion coating is a chemical treatment applied to steel parts that creates a thin adhering layer of iron, zinc, or manganese phosphates to improve corrosion resistance or lubrication or as a foundation for subsequent coatings or painting It is one of the most common types of conversion coating. The process is also called phosphate coating, phosphatization, phosphatizing, or phosphating. It is also known by the trade name Parkerizing, especially when applied to firearms and other military equipment.^[5]: 393

A phosphate coating is usually obtained by applying to the steel part a dilute solution of phosphoric acid, possibly with soluble iron, zinc, and/or manganese salts. The solution may be applied by sponging, spraying, or immersion.^[6] Phosphate conversion coatings can also be used on aluminum, zinc, cadmium, silver and tin