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

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

Nisar Ahmad
- Lahore Pakistan
November 3, 2022

Closely related historical posts, oldest first ...

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

To minimize searching & thrashing, multiple threads were merged; please forgive repetition, chronology errors, or disrespect of other responses (they probably weren't there) :-)

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

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

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

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

← Ed. note: Readers, please describe the details of your own situation Huh? Why?

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

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