Pin holes on e-coat bottom surface
August 16, 2011Q. Hi Sir,
I'm an employee of a plating house. Recently my company newly fabricated a 2.5 tonne e-coat tank to relieve some production capacity. Unfortunately, every model go through e-coat surely will have plenty of pin holes at bottom surface. Please be kind enough to give me some idea what setting gone wrong in my tank. Thanks
plating shop employee - Ulu Tiram, Johor, Malaysia
A. Maybe it's the angle from which the photo was taken... but I can't see a weir to remove the surface foam being produced by the coating process?
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Terry Hickling Martex Paints Ltd  Birmingham, United Kingdom |
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August 19, 2011
A. Bubble on top of coat bath. You need a weir box to roll the top of the tank to. You also need to determine where the air bubbles are coming from.
Adam Adkisson- Mission Texas
First of two simultaneous responses -- August 22, 2011
A. Bubbles can be produced by cavitations in the main tanks pumping system.
Where a side tank is used for both collection of the e-coat tanks surface bubbles and the addition and mixing of new tank material, a bubble producing problem is possible if the weir shoot tank is:
a)Too small.
b)The rpm of the internal mixing system (normally a stirrer) is too fast.
c)Blades of stirrer are too low.
Martex Paints Ltd
Birmingham, United Kingdom
Second of two simultaneous responses -- August 23, 2011
A. The foam issue already resolve, mainly due to circulation pump choked by some cleaning cloth. However, the problem I'm facing is happening some pin hole due to gassing at bottom surface of raw parts.
Parameter of ED in spec; just pH slightly acidic (pH 4.5 - 5.0). What I'm curious is just whether tank either circulation not enough or maybe tank setting something been neglected...Maybe I'm wrong, kindly advise any eval'n that I can find out more.
Thanks
- plating shop employee - Ulu Tiram, Johor, Malaysia
October 30, 2011
A. Most important to avoid pitting at the bottom - clearance of work piece to bottom sparge pipes should be minimum 200 mm!!!
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November 1, 2011
A. Hi KC.
I once had the opportunity to look at an ED film ( 40 X I think) before the curing process and 'lo and behold ', they were full of pin holes! It is only through the curing process, the higher temperature makes the film more 'fluid', those pin holes were closed up, so to speak.
It may be possible, your pin holes problem are curing oven related rather than ED tank related??
- Penang, Malaysia
November 27, 2011
A. First ensure that all the bath parameters are within specification and pH meter, Current-voltage meters are working properly.
Pinholes at the bottom of tank may be due to excessive gassing i.e. due to high current density which further may be due to high solid content or suspended particles or too low pH.
Also,get solvent content tested by your paint supplier.
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Manoj Kushwaha plating & painting - Rampur, India |
January 25, 2012
A. Check your solvent (BC) content. If it is on higher side it will definitely create pin holes. Check also ramp up time for rectifier voltage.
Manish Dhyani- Noida, India
February 1, 2012
Kindly provide details of the pre-treatment process that is done prior to E-coat.
Have you checked the component after pre treatment and before E-coat for presence of oil on its surface?
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Gurvin Singh Coatec India - Mohali, Punjab, India |
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March 21, 2012
Hi Folks,
Thanks for your advice,. I already go through all recommendations but it was not root cause. Thereafter, I changed existing circulation pump from Vertical to horizontal centrifugal type. Surprisingly, it resolved all those pin hole defects.
Anyway, thanks for ideas from all.
Regards
- Ulu Tiram, Johor, Malaysia
June 18, 2012
Q. We have pinholes after applying the electrodeposition coat.
We think we have a problem in the activation process in pretreatment line. Please guide me.
Thanks
- Tehran, Iran
July 14, 2012
Q. How to Solve Pin holes in CED paint plant. Please give detailed answer.
Senthil Kumar- Chennai, India
A. Hi Senthil.
As you see, we appended your inquiry to a thread which may already answer it. If not, please give detailed question. Thanks.
Regards,
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 Ted Mooney, P.E. RET finishing.com Brick, New Jersey |
November 16, 2012
Q. dear sir,
I am working as an Automotive CED Paint plant, in our plant daily pinhole, crater and white dot issues observed after oven, daily more rejection, all parameters within spec. so pls give some ideas to resolve this issues.
- Chennai, India
