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MEQ vs pH in CED bath. Paint conductivity is dropping/rising

Q. Kindly suggest with maintaining pH-7 & conductivity-less than 10; if possible suggest some ideas.
We have recently changed the resin of the mixed bed, but are not able to get a stable pH & conductivity during the CED process.

Rudra Ind
- Lukhnow UP, India
July 30, 2023

⇩ Closely related postings, oldest first ⇩

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Q. What is the relation between MEQ (milliequivalents) level & pH of the CED BATH.

Please offer the equation relating these two parameters.

Sir, I am getting higher DFT with even a degree rise in bath temperature, Why?

Conductivity 880 siemens
Bath parameter pH 5.35

Voltage 150V

Temperature 26 & DFT 28 - 33 Mic

Temperature 28 & DFT 32 - 40

T. Srinivasan
paint shop - Chennai, Tamilnadu, India

A. Actually, quite a feat. Normally, one would expect a coating of 15 micron ± 2 micron.

As for the relationship with temperature, the thumb rule is one degree is equal to one micron. But do not read this thumb rule in isolation. Coating thickness is also related to NVM, pH and conductivity besides other factors.

But before we try and answer that please post more details of what is being coated, how much coating time, and supplier of E-coat paint.

Gurvin Singh
Mohali, Punjab, India

A. Coating thickness can vary if the area of components will vary and we put same voltage -- so area should also be seen to control DFT.

R B Singh
- Faridabad, Haryana, India
July 24, 2015

Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)

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Q. If conductivity of CED bath is reduced up to 400 microsiemens and pH is 6.2 , then what happens in the coating? Then how can I increase conductivity?

My CED bath level is reduced daily after some processing of articles. How can we maintain bath level? (NVM % is within the limit)

Naresh Shudra
Rexnord - Mumbai, India

A. At a pH of 6.2 you should have a paint kick-out!

Simply add the pH controller supplied by the paint supplier and your pH will fall within range and the conductivity will go up.

Your paint supplier should be able to help you on that.

Gurvin Singh
Mohali, Punjab, India

thumbs up signThank you Mr. Gurvin, but my pH is within the limit.

Naresh Shudra [returning]
Rexnord - Mumbai, India

? What is the your resin character?

Dr Halim Polat
- Istanbul, Turkey

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Q. Hi everybody.
I've experienced almost the same issue lately!
Although all CED bath parameters have been in the range as below, the conductivity of CED paint gradually decreased from 1600 to around 1000 value.

NV: 15%
pH: 6
MEQ: 38

Moreover, we couldn't find any UF drainage or bacteria attack!
Your response would be highly appreciated :)

M.M. Barfehi
- Tehran, Iran
November 25, 2016

A. Your MEQ & pH value are not in proportion. Please check again.

Avnash Vidhate
- Nashik, India

"Electrophoretic Deposition (EPD)"
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Q. My name is Thomas and I've been having problems with high conductivity in my PPG paint bath can you please tell me what I must do to get a lower conductivity level?

Thomas Hudson
- Anderson, Indiana
November 15, 2019

A. Send some ultrafilter permeate to drain and make up the volume with water. This may take several days to get back into range. Most importantly - find the source of the high conductivity. (i.e. drag in from pretreatment.)

Dan Mack
- Horicon, Wisconsin

? What is the pH of your paint in the tank ?

Avinash Vidhate
- Nashik, Mahatashtra, India

"Electropainting: A survey of principles and practice"
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Q. My CED bath conductivity is decreasing daily. How can I increase conductivity of CED Bath? Please give me a suggestion about this.

Archana Dhapse
- Pune, India
October 1, 2020

? What is your CED bath pH value ?

Baljeet Singh
- Ludhiana Punjab, India

Q. pH value of CED Bath is 5.46

Archana Dhapse [returning]
- Pune Maharatra
November 12, 2020

by Rodger Talbert

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Q. CED bath conductivity is low ... how to increase?

Sagar Patel
- Rajkot gujrat
June 7, 2021

A. Good day, Sagar Patel!

First, follow the parameters and limits of the E-paint supplier.
To increase the conductivity of the E-paint in the bath:
1. increase the resin and paste content, solid and p/b ratio go up.
2. check the pH of E-paint, decreasing the pH increases the conductivity.
3. check the solvent content, increasing the solvent increases the conductivity.

What changes in the quality of the coating do you observe at low conductivity?

Dmitriy Belanovich
- Minsk Belarus

Q. How to perform Acid MEQ of CED Bath manually?

Nisar Ahmad
- Lahore Pakistan
November 3, 2022


1. Analytical balance (capable of weighing to an accuracy 0.01 g)
2. Magnetic stirrer with magnet.
3. pH meter with stand.
4. Burette 25 ml with stand.
5. Potassium Hydroxide (standard volumetric solution (KOH) = 0.1 N in Deionized water).
6. THF (Tetrahydrofuran)
7. Butyl Cellosolve for electrode cleaning.


1- Clean the electrode of pH meter with butyl cellosolve and rinse with Deionized water and calibrate the pH meter with pH standard solution (buffer 4.0 and buffer 7.0).
2- Record the weight of empty beaker (W1).
3- Add sample into the beaker and record the weight (W2).
(quantity of the sample is mentioned in the table below)
4- Add approximately 60 ml of THF (tetrahydrofuran) reagent.
5- Place the beaker on magnetic stirrer.
6- Dip the electrode of pH meter in above sample solution.
7- Titrate it with 0.1 N KOH standard solution until the pH achieved 10.
8- Record the volume (ml) of 0.1N KOH consumed for titration (T1).


MEQ Value = T1 x Normality of KOH X 100/(W2-W1) x NVM%/100

Asim Mushtaq
- Lahore Pakistan
October 7, 2023

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