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Steel preparation for powder coat

We manufacture steel toolboxes and am looking for the best chemical to put in a wash cabinet to clean the oil and grinding dust off the steel prior to powder coating.

Is a phosphate the best option? or is there something else we should look at.

Vince Koehn
manufacturing - Montezuma, KS, USA
2005

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2005

Vince

The best approach is to plate alk cyanide free zinc, chromate and paint...
Your boxes will last. and this is not expensive .. Its cheaper than a lot of phosphate and rejects.

The US has comapnies that make the chemicals you want. take a look and I am sure you will benefit once you find a chemical process provider.

Regards

Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016

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First of two simultaneous responses --

Hi Vince,
Let me start off by saying there are many companies out there making toolboxes that successfully use iron phosphates prior to powder coating.

If you have a one-stage cabinet washer, then you must use a detergent iron phosphate because you will need to remove organic materials and the detergent in the product will do that.

If you have more than one stage, depending on how many stages you have, you can employ alkaline cleaners and seal rinses. Again, it depends on the number of stages you have.

And, the quality of the powder coating also plays a big role in the overall quality of your toolboxes.

Good luck!

Bill Duttlinger
- Naperville, Illinois
2005

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Second of two simultaneous responses --

The above recommendation is the absolute best advice for quality, but I doubt you can get a high enough sales price to pay for all that unless you have the boxes manufactured in his country at their labor rates.

If you do chromate, be sure to leave the chromate very thin as it is a water bearing gel coat which will dehydrate and fall off at powder coating baking temperatures.

If you must manufacture and sell in the USA, just put on a light iron phosphate made-up with D.I.water, followed by a chrome rinse (2 av oz Hex Chrome per 100 gallons of D.I.water).

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

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I mostly agree with you, Mr. Probert. To do zinc plating underneath powder coating may be a fine finish, but it is expensive and it may be overkill for this application.

On the other hand, your reply sort of implies that a strategy to compete against low labor cost competitors is to reduce the quality of the finish, and ask the consumer to choose between two competitively priced units: a very high quality Indian product or a lower quality American product.

There may be no way at this late date to save American industry and prosperity, but offering a lower quality product at the same price seems to be the fastest possible path to extinction :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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2005

FOR STEEL WORK
WE RECOMMEND ALSO THE IRON PHOSPHATING (THE PHOSPHO-DEGREASING FORMULATION)
BUT ACCORDING TO THE TYPE OF STEEL TRY TO ADJUST THE OPERATING CONDITION OF THE BATH
AS EXAMPLE :
IF YOU WILL USE IRON PHOSPHATING ( MO ACCELERATOR )
ADJUST THE PH AS FOLLOW
FOR COLLED ROLLED STEEL 5.4 - 5.8
FOR HOT ROLLED STEEL 4.5 - 5.2
TO GET A GOOD (BLUE GOLD VIOLET GREY) COLORS OF AMORPHOUS PHOSPHATE

Ahmed Fouad Serag Eldin
Ein Shams - Cairo - Egypt

Apart from phosphating, shot blasting of the surface to Sa 2.5 to Sa 3 finish should give you a clean enough surface that provides excellent substrate for powder coating.

Srinivasan Subrahmaniyan
- Indore, India
2005

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Your opinion is welcomed and appreciated, Srinivasan, but I don't think I agree with it. Phosphatizing is a better pretreatment than sandblasting.

Ahmed Fouad Serag Eldin
Ein Shams - Cairo - Egypt
2005

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Dependent upon the amount of touch-up you are going to be doing in the faraday areas, you might want to look at the beefier pretreatment because the only thing that is going to save the bare areas that get spray painted from early failure would be the pretreated steel.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2005