Metal finishing Q&As since 1989

-----

Set Up of a 5 Stage Powdercoating Pretreatment Line with RO Water

January 19, 2011

We have a 5 Stage Iron Phos pretreatment line which we are converting over from city water to RO.
Should all stages use RO water (rinses and chemical baths) or should we have some stages city water and some RO. Our RO system is big enough to feed the entire line.

Line layout
Cleaner
Rinse with halo
Iron Phos
Rinse
Rinse with halo

Thanks
James

James Starling
Engineer - Ontario, Canada

---

It seems logical that tank 4 is towns water and partially fed by the over flow from tank 5.
However, this suggestion comes not from a powder applicator but a powder supplier and we will see what the trade experts suggest.

Terry Hickling
Birmingham, United Kingdom
First of three simultaneous responses -- January 20, 2011

---

You have spent the money for the RO system. It does not cost that much to use it and your tanks will last longer and your rinses will rinse better.
As far as city water goes, in a town 30 miles away they have one well that is nearly distilled water quality and another well about 10 miles away that is as hard as an artesian well, so it makes a huge difference what your city water quality is. Besides the chlorine and the fluorides that are added will not do your line any good.

James Watts
- Navarre, Florida
Second of three simultaneous responses -- January 20, 2011

If the RO system has a capacity large enough to feed the entire washer, I say use RO in all stages. It will help your rinse stages last longer and will eliminate the possibility of scale buildup in any of the stages. Our 5-stage washer used to be set up like yours with the two rinses and a halo at the end but, then we changed the 5th stage to a non-chrome seal. It gave us a few extra hundred hours on our salt sprays. Doing this we lost the counterflow from stage 5 to 4 but, the better salt spray results were worth it.

Adam Krey
- Whitewater, Wisconsin USA
Third of three simultaneous responses -- January 21, 2011