The authoritative public forum
  for Metal Finishing since 1989
-----

Zinc phosphate sludge

The heat exchanger on my zinc phosphate tank gets plugged with sludge. Is there any way to clean this without taking it apart or nitric?

Ed Petermann
- Cambridge, Ontario, Canada
2003

---

Ed,

The only method I know of are the one's you mentioned. I have the experience that the engineering and the construction of the heating system has a very great impact a) on the frequency of plugging and b) on the "cleanability" of the system once it is plugged. A good design can prevent the plugging for a very great deal thus reducing your maintenance costs. A closer look at your actual system and a possible re-engineering is where I would go for.

Good luck,

Remmelt Bosklopper
- Enschede, The Netherlands
2003

There is a method of preventing the sludge from ever buildup in the heat exchanger. We have a johnson valve that never lets the differential get more than 15 or 20 degrees higher than the zinc phosphate. that is being heated. prevention works best. the higher the differential the faster you form flakes in the heat exchanger. I cleaning one tonight where this rule was ignored. If you stay within 15 or 20 degrees you can go a year without taking it apart and acid cleaning the plates. good luck

Denny
- Peru, Indiana, USA
January 26, 2011