Where the
world gathers for metal finishing
Q&As since 1989


-----

Spray vs. steam wand for iron phosphates

I am interested in comparing of spray wand vs. steam wand equipment for iron phosphates. Which type of system works better to phosphate parts, which uses less water etc. The parts being phosphated are a variety of shapes and sizes. The soils encountered are synthetic oils and orbital grit media. Thank you for you help.

Diane Patterson
- Oklahoma City, OK
1999

---

Diane -

Steam phosphatizing has always seemed to work best. The temperature assists in the coating formation and the inherent pressure of the steam gives a cleaning assist. Remember that steam phosphate coatings don't have to be at 212 degrees, they can be as low as 140 F. Be sure your cleaner/phosphate has a suitable cleaner package for your soils and do some experimentation with time/temp of solution on parts.

Good Luck.

Dan Brewer
chemical process supplier - Gurnee, Illinois
1999

---

This is a question of soil for me. You cannot achieve the impingement of a 1500 psi pressure wash system with steam, so which is more important in removing the soil: A) temperature (i.e. melting grease or other lubes) or B) impingement to remove particulate and other heavy soils?

You'll remember that you cannot phosphate a dirty surface, so with any wand system it's all about getting the surfaces clean, so that phosphating can take place. Sure steam systems may use less water at higher temperatures, but is that really what you want? One of the serious downfalls of a good wand system is in adequate flow and rinsing.

You can lay down the best phosphate coating in the world, but sometimes when the conditions are just right, the residue left behind due to incomplete rinsing will cause paint failures. Why? Paint sticks well to phosphate that sticks well to the metal. Loose crystals and the sludge of incompletely formed phosphate coatings break away easily from the metal, but stay attached to the paint. Ever see a perfectly good paint chip right off the part for no reason...

Got to get cleaning first, then adequate rinsing is a must, follow with a sealer, if appropriate (a topic too long for discussion here), then paint...

  
Craig Burkart
- Naperville, Illinois
1999