Topic: Pretreatment process for Steel

Hi, I am pretty new to the powder coating industry and i'm getting some bigger clients in day to day.

I'm in the process of getting a pretreatment setup going. My main concern is to setup something that is small at the moment.

I have a batch oven and i need to setup the pretreatment station to do steel newspaper racks for a customer. I currently have the phosphate chemicals to do so.

How does the setup need to be? Example: (1) Degreaser (2) Water Wash (3) Phosphate (4) Water Wash.

Or could i just go to Degreaser,Phosphate, then wash? Or will that contaminate the phosphate?

Any advice from those who have first hand experences in this would be GREAT!


Re: Pretreatment process for Steel

Here is an example to introduce the general idea. A Powder coater asks in a 'Finishing Fourm' from 'Product Finishing Magazine'...

"Doing steel newspaper racks in P-coat and asks..."How does the setup need to be? Example: (1) De-greaser (2) Water Wash (3) Phosphate (4) Water Wash." "Or could I just go to De-greaser, Phosphate, then wash? Or will that contaminate the phosphate?"

skip talking here. Wire is hard to clean, what with embedded drawing compounds that cool the die such as wax, powdered lime, heat treating smut, scale from the steel, general high Rockwell hardness and once powder coated, shipping this stuff unscratched is a pain, ect. Skip did a wire rack p-coat line in Chicago for a guy who made display end cap fixtures for magazines in food stores.

The fast answer: If your buying a conveyorized direct or indirect gas fired or steam heated power spray or immersion dip five stage or three stage washer a durable and 'waranteed finish' can be achieved. A wand will produce a 'point-of-purchase' finish.

A skipisum~Your competition will provide this if you don't...but $'s are tight so...we dream.

15 second entrance vestibule

60 second hot spray wash. Vee jet nozzle.

30 second dwell*.

30 second a m b i e n t spray rinse. Vee jet nozzle.

30 second dwell*.

60 second hot spray iron or zinc phosphate. Full/hollow cone flood jet nozzles.

With zinc you'll need some sludge settling/filtering/stuff.

30 second dwell*.

30 second a m b i e n t spray rinse. Vee jet nozzle.

30 second dwell*.

15 second a m b i e n t spray seal coat. Vee jet nozzle.

30 second dwell*

15 second Deionized Water rinse. Fog/Mist nozzle.

15 second exit vestibule

*I should say a dwell is to drain and not cross contaminate the next tank. 1/3 pitched back to the last tank and 2/3 pitched fwd to the next tank. Be aware of flash rust. May need a fog/misting nozzle to keep the work wet in the dwell area.

Dry-cool-powder coat-dwell in heat**, impinge for cure-cool-off load. **turn the powder shiny in a unblowen hot area before the cure oven recirculation fan hits the work.

Ask wire rack prospect turned into a customer this question.

A skipisum~How good is good?

Do we need just a point-of-purchase powder coat job or a warranted finish to some spec. What are the specs? What does the customer want in terms of coating performance? What about UV? Thermo set or thermo plastic powder, or a soft touch coating? Indoor or out door? Polyester blended powder? Hammertones? Gloss?, Scratch, bend, pull, reverse, salt spray tests...how good is good? My guess is cheap and dirty.

Now some common sense, this is the easy part.

SWATCH Soil Water Action Time Chemical Heat.

Stage #1 Say 60 seconds, hot; Generally a small batch curing oven may have a small manual spray wand shooting a chemical soap heavy with surfactants to surround and remove soils and make it not possible to reattach the soils back on to the work.

Since water floats atop oils it is imperative to remove these oil types of soils prior to cleaning the work. A hand wipe may be necessary to start with..

A skipisum~Like solvents remove like soils. So figure that out.

With a de-soiled substrate achieved, this concoction of oils, soils, and soaps must be removed. Usually by copious amounts of rinsing with a pure water as possible, free of grains of hardness to limit water spotting. Do the water break test on the work or a equally soiled test panel. If the water breaks, it ain't clean enough.

Now that the water born phosphate chemicals can 'see' the wire work an iron phosphoric crystal structure of about 130 mg/sq ft can be applied in a hot spray application. How does this work? The phosphoric acid dissolves a wee bit of the black iron [mild steel] wire and re-deposits itself back onto the work, forming a grey matt finish that chemically is bonded to the substrate in the form of a crystal coating that provides a 'bed' for the coating to stick to.

A skipisum~Paint does not stick to steel, phosphate sticks to steel and paint sticks to phosphate.

Rinse off the loose crystals

To fill in between the crystals with a seal coat.

The work ought to be rinsed with D.I. water or R/O water.

Well that will get you started. Find a little 'steam genny' to make hot water, the right chemicals, a well worked out process, a wand or two and a guy who doesn't mind getting wet in the spray booth and go paint some news paper racks before no more news papers are printed and we read all our news on the web.
How's the batch oven?
Last edited by skip (Today - 07:15 PM)
"Your Best Finish Starts Here"

Last edited by skip (12/28/2009 - 03:50 PM)

Your Best Finish Starts Here


Re: Pretreatment process for Steel

I have a new pretreatment technology now available commercially (finally) that you may find useful. I refer to it as a hybrid pretreatment with equivalent or better performance versus hexchrome. It utilizes a passivating technology with a tenacious binder technology that readily accepts a huge range of paint types. The intercoat adhesion is tremendous and topcoat gloss is typically increased.

1)Clean, 2)Rinse, 3)Hybrid Pretreat, 4)Heat Activate @175-400F,5)Paint/Coat, 6)Cure, Done. A full color pallette has also been developed for this. Samples are available.

Feel free to respond in kind if you feel this hybrid inorganic-organic system is of any interest. It has passed trial phases.


"little company, big ideas"


Thank you!



Re: Pretreatment process for Steel

Unique 1,

Unfortunately, using the phosphate directly behind the degreaser will not do well. A clean rinse is very important.

A good process would be:


fresh water rinse

phosphate 30-60 seconds

fresh water rinse

I hope this helps. Please let me know if you need any help getting the right chemicals in your facility. Good luck.

EnviroServe Chemicals, Inc.

(910) 892-1791