Pretreatment Duration
Q. I have seven tanks in the pretreatment process I use for my
batch powder painting operation:
1. Degreaser
2. Water
3. De-ruster.
4. Water
5. Water
6. Zinc phosphate
7. Water
Can you please give me some advice on how I can
shorten my pretreatment time?—L.M.
A. Unfortunately, what you have listed are the minimum steps
that are necessary for a conversion coating. Possibly, the
segment that offers any possibility to shorten the overall
cycle would be if you could eliminate the de-rusting step.
This would only be possible if you could control and elimi-
nate the rust from your upstream manufacturing process.
First examine the incoming parts or sheet material. Are
they coming in the door rusted? If so, can you work with
your suppliers to change this or have them perform the
de-rusting before you receive the parts? If the rust is occur-
ring within your manufacturing process, you can work to
eliminate it through the use of in-house light oils or indoor
corrosion inhibitors and reducing the amount of in-process
time the parts are allowed to sit between processing steps.
Chrome Pretreatment
Q. I am the chrome specialist for a large automaker. Do you
have any leads on effective pretreatments to chrome and for
painting over the chrome? We do use several platers that use
pretreatments to chrome before painting. But, in a general
sense, do you have any experience with what does and does
not work?—J.R.
A. Generally, you need to effectively clean your parts prior to
any chrome plating. This may involve the use of an alkaline
electrocleaner with a periodic reversed current. This would
be followed by thorough rinsing and possibly the use of a
dilute acid cleaner with rinsing to neutralize any residual
alkaline cleaner. Some shops will first do a copper plating,
while others will go directly to the nickel plating. Regardless,
either process will require a nickel plating to provide a good
base for the chromium as well as good corrosion resistance. I
am not sure what processes need to be followed to paint over
chrome plating. Generally, you would not spend the money
on the chromium plating only to paint over that surface.
toll-free: (866) 424-7252
www.airblastinc.com
sales@airblastinc.com
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PRODUCTS FINISHING — pfonline.com
39
PARTS CLEANING
C L I N I C
Cleaning and Pretreatment Zone
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