Heaters for Phosphate Plating Tanks
Phosphate coatings are applied to ferrous parts to increase their corrosion resistance. There are several different ways to heat a phosphate plating tank. Down Draft gas burners in a immersion tube system are used to heat large tanks of +2000 gallons, Double boiler tank with PTFE (Teflon) liner or electric over-the-side and L-shaped or bottom immersion heaters.
These electric immersion heaters feature 316 stainless steel or Titanium sheath or are PTFE coated. An added benefit to the heater would be to electro-polish (optional) the sheath. This process reduces the micro structure of the tube to a shiny finish giving the solution reduced surface area to build up on.
Most heaters have a heat output of 35-40 watts per square inch (WSI). By de-rating the heater, the watt density is reduced to 20 WSI. This design slows the chemical buildup process on the heaters. After 2-3 weeks the heaters must be pulled and cleaned.
In selecting heaters the first criteria is to know phosphate plating tank depth. Because of the high solution evaporation rate of ¼” to ½” per hour, we recommend L-Shaped- or Bottom immersion heaters, especially for polypropylene plating tanks. Over-the-side- heaters can be used, but be conscious of solution displacement with the parts in combination of the evaporation rates.
If you are using a polypropylene tank, then this is the heater of choice. Add a temperature control system with a manual reset level safety shut off and install a liquid level control.