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Reduce paint thickness in Cathodic Electrodeposition (CED) system?
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2005
Q. Hello sirs I humbly feel that it's really a great time to interact with you wizards. In our CED process, we are encountering a major paint problem poor E'coat deposition (dipping process) defect in the sill outer panel of the car body because of "rust" in the non-coverage area of coating. This is not occurring in the sill outer panels we use which are provided with wax holes.
I'm really baffled whether the problem is with the process parameter settings or the mechanical alignment or settings. The process parameters settings we use in our CED process are :
%NVM = 18.7
pH = 5.94
CONDUCTIVITY = 1827 uS
P/B RATIO = 0.16-0.25
BATH TEMPERATURE = 30.7° C
APPLIED VOLTAGE = INLET POINT = 0 V
OUTLET VOLTAGE = 100 V
MAIN BUS = 235 V
CURRENT = INLET = 0/350 amps
MAIN = 950 amps
When we change the inlet voltage, paint defect "hash marks" start appearing in the car bodies. We are planning to increase the %NVM or the inlet voltage -- WILL IT SOLVE THE PROBLEM?
Generously give me your valuable suggestions .
Looking forward with great regards ,
- Chennai, India
Q. I WANT INFORMATION ABOUT CED COATING. I WANT CED COATING CHEAPER THAN POWDER COATING
YASEER charoliaplating shop - MUMBAI INDIA
March 17, 2011
Q. Dear sir,
How to increase MEQ if bath pH is already lower side?
- Greater noida
February 27, 2012
Q. I am a technician at a factory in Shah Alam. I run the factory's CED process. I have a problem with the quality of the paint. Each item of the CED process is bubbled on the surface of part. Why did it happen?
Khairul Abidin Mohamed- Shah Alam, Selangor Darul Ehsan, Malaysia
March 1, 2012
A. Check suction of circulating pumps after shutting the pumps.
See if there is any leakage.
- Nasik, Maharashtra, India
June 7, 2012
Q. I have been given a project to optimize the DFT of e coat. I need to know the exact chemistry behind e-coating plus how much it varies according to the pH, NVM. I know how it varies I just want to know how much it varies. For example, at 21% nvm at my current bath conditions I'm getting about 19 microns and for 18% I'm getting 16 microns DFT. Please help ASAP.
Harsh Bhatiapaint shop, prod. - Pune, Maharashtra
July 10, 2012
Q. I have recently been given to work on DFT optimization of paints in top coat line and on CED DFT optimization. Please suggest me any ideas on how to proceed with this project?
Vikrant Patnaik- Ahmedabad, India
September 14, 2012
Q. What will be effect of higher DFT on CED coated part (40-45 micron against specification of 18-22 micron) on product quality?
Application : Wheel rims
Coating: CED + Top coat (white /silver)
- Bhoapl, India
April 11, 2013
A. It leads to peeling off.
Vijay Bhadwaj- Ludhiana, Punjab, India
May 20, 2013
Q. Hi, I wanted to have input from you all ED experts out there!
We have a car production line with different models, surface area of which differs.
End result is that the largest body gets the required DFT with voltage of 360V, however our challenge is to optimize the energy requirement for all models. We are thinking of a Variable Voltage Rectifier, i.e., to vary the voltage to meet required DFT for DIFFERENT surface areas.
Is having this system a good idea? Can you share some more ideas of optimizing for different models? THANKS.
- Lahore, Pakistan
May 23, 2013
A. The voltage can be controlled automatically so that the DFT remains the same even when the surface area changes.
Gurvin SinghMohali, Punjab, India
July 29, 2013
Q. Hi, I have a cathodic electrodeposition painting system for painting motorcycle frames and other fabricated items. But now I am getting some coarse and nonuniform film on the part. Film thickness is not uniform and on some flat surfaces the film is coarse like deep orange peel. Thickness in some places is 25 microns and some places 70-100 microns. Condition of CED bath and other stages are almost the same as when no problems occur. What may be the cause of this problem and what is the remedy?
Please do a favor to me by giving me the proper solution to this problem.
Thank you.
- Gazipore, Dhaka, Bangladesh
December 20, 2013
A. To reduce the thickness of the coated film you have to add hydrogen peroxide to the bath in the range of 1-10%; it acts as a hydrogen scavenger. Hydrogen gas evolves making defect in the deposited film like pits and makes the surface non uniformly covered -- the problem is in the hydrogen gas evolved, you can use other scavengers like nitroethane.
I think this is the method to get uniform and reduced thickness.
Thanks
- cairo egypt
February 23, 2016
January 23, 2014
Q.
The data parameter from my process are :
1. NV 14.54% range 13-15
2. Coating voltage is 140 V (range 130 to 300 V)
3. pH is 6.33 (range from 5.8 to 6.4)
4. Conductivity is about 1630 micro Siemens/cm. (standard is 1100 to 1600).
5. Ratio F1 to F2 is 1:10
6. MEQ 32.7 range is 28-32
7. Solvent content 1.2 range 1.1-1.4
I found abnormal surface finish now like sagging is occur and in some point no paint is adhere to the metal. also in some area DFT is abnormally high. what to do now ?
More clearly I want to know:
1. how can I reduce conductivity of ED chemical and
2. how can I reduce pH or ED if it goes higher than the range?
3. how can I reduce MEQ ?
I also used the latest technology of ED Paint, which is Acrylic CED-Lead Free
- Dhaka, Bangladesh
A. Welded area usually having spatters and gloss bleed. It will not allow CED coating/paint to stick to the surface over a period of time rust formation will happen.
It is very important to clean the weld spatters & gloss bleed before any paint coating.
For reducing ED coating (CED DFT) you may reduce the bath temperature to less than 25 (22 - 25) & voltage (140-180)
- Mysore, Karnataka & India
August 24, 2016
Q. What is the effect found on surface when pH value of bath increases or decreases?
Suman K Singh- Jamshedpur, Jharkhand, INDIA
July 25, 2016
"Electrocoating: a Guidebook for Finishers"
by Electrocoat Association
on
AbeBooks
or
eBay
or
Amazon
(affil links)
A. Hi Suman. "Handbook of Electropainting Technology" has at least 6 sub-chapters devoted to pH; I don't have a copy of "Electrocoating -- A Guidebook", but good books on the subject are best when you are interested in the abstract science of a subject. Vendors might be able to meet with you as well to discuss such general topics as well.
This forum handles highly specific shop problems well, as you can see, but there probably isn't much that people can do for you in a forum of this type to help with abstract theoretical discussion.
If you are having a specific problem, please carefully detail it (i.e., use more words in your question than you want in the answer), and I'm pretty sure the readers can help. Good luck!
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 2016
Q. Hello sir,
I am rohit singh. Currently I am starting of career in CED coating so please suggest me best book, or if can be possible you provide me related material.
Thanks,
Regards,
- gurgaon, haryana, India
December 9, 2016
A. Hi Rohit. The two that I just mentioned to Suman are the only books I know of; I've only read the one. Good luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
"Handbook of Electropainting Technology"
by W. Machu
on
AbeBooks
or
Amazon
(affil links)
Q. Sir, I am working on CED machine. On the finished product I get a thickness up to 80 mm, but only 15-20 is acceptable. So what to do for this?
Rohit kumar- faridabad,haryana, India
September 9, 2017
A. Hi cousin Rohit. This page is about how to reduce the thickness of CED coatings. There have been some explicit & repeated suggestions, so please try your best to cast your question in terms of the suggestions that have been offered and commenting on the proposed solutions. Thanks!
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 2017
Q. Running Cathodic epoxy e-coat line. My paint thickness is through the roof. I have turned down our rectifier and still no better results.
Jason Daire- Jackson, Michigan United States
April 25, 2018
Q. Hello friends
Please can you help me for CED coating DFT because currently I'm facing DFT problem. I'm getting high DFT 18/20 micron, as per required DFT 16 micron. So please suggest to me CED bath parameters is temp. 32 and NVM is 14.63, CED bath pH is 5.9. And anolyte conductivity is 1400, and CED bath level is 18/20. Rectifier is 200 V.
Best regards
Student - Jamesdpur, India
September 26, 2018
December 15, 2018
A. Hello jason , Hello amit,
I think you both have same problem with excess throwing; I think three ways we can decrease the DFT:
1) Decrease paint solids
2) By Decrease in pH (5.5- 5.6)
3) Addition of solvent which reduces the viscosity of tank
So by this way we can control on DFT
Chandresh Varsani
- RAJKOT, Gujarat, India
August 18, 2020
⇦ (tip: readers rarely show interest in abstract questions, but people's actual situations usually prompt responses) 
Can we reduce the acrylic DFT from 25 to 20? Or how much DFT can be kept of a CED coating at the lower side, on which all the Quality properties are right? (Current Spec is 25-30 Micron).
Sunil kumar- Haridwar Uttrakhand
A. Hi Sunil. I don't think your concern was actually about UV resistance, so we moved your posting off of the thread where you posted it, and onto this page which is about controlling thickness, and which already offers many suggestions. It sounds like 20 to 25 micron thickness is generally readily achievable.
But if the spec says 25 to 30 microns why are you anxious to change it? What is the substrate material and its surface roughness? A thickness which is sufficient for a polished substrate may not be satisfactorily pore-free on some rough surfaces. What follows the CED? -- Powder Coating? What precedes it -- a reliable zinc phosphate? Thanks!
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 2020
"Electrocoats: Formulation and Technology"
by Bruggemann & Rach
on
AbeBooks
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eBay
or
Amazon
(affil links)
Q. Dear Sir, I'm the PTED line Operator.
Sir I want to know how I can reduce thickness of CED paint.
Current pH = 5.8 to 5.96 while std. pH = 5.8 to 6.20
Anolyte conductivity is 800 to 810; sometimes it's 790 to 800 wile standard of anolyte conductivity 700 to 1200.
And also bath conductivity is also low as compared to before. Current bath conductivity 1550 to 1580 while temp is 28 to 28.8 while std temperature of ED is 28 to 30 while voltage is setting on 270 to 290.
First we worked on 290 voltage but now we reduce voltage to 270 to reduce thickness, but still not achieving from 40 to 25.
How can I reduce thickness? Kindly suggest ... I'll be waiting for your reply.
- Pakistan Karachi
A. Dear sir,.
Please check the solvent content in bath, if it high ,
By reducing the solvent content in the bath DFT also will reduce
- Hindupur, Aandra pradesh
May 31, 2021
May 2021
Thanks Sudhakar! Five previous writers offered the same relationship: "lower solvent = lower DFT". It's a bit counter-intuitive because higher solvent does means lower viscosity as one responder noted ... but competing forces overwhelm that effect as confirmed by graphs in the previously mentioned W. Machu Handbook of Electropainting Technology.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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