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Cratering problem in CED electrocoating?

Q. 1 ) I am facing craters problems in CED coating.How to rectify this problem. I have two options a) By increasing paste(pigment) b) By using oil filters once in a month to remove oil(if it is there) I want to know what other methods to solve this problem. I am using advanced CED system which is used everywhere in the world and I am maintaining all parameters but still I am facing this problem.

2) How to rework a CED coated component?Is there any method other than first stripping the paint(with a paint stripper) and then again paint it?

Manish Chandra
- New Delhi, India

"Handbook of Electropainting Technology"
by W. Machu

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A. You have so many problems, what is your paint supplier doing. You need to see if a new paint supplier is what you need.

Pitting can be caused by oil in the bath or oil on the components. You have to identify the point of contamination and eliminate it.

Coat standard panels to see if the bath is contaminated. If not, then work on the pre treatment line. If yes, decontaminate the bath and simultaneously work on the PT so that further contamination is avoided. Also check if the bath is getting contaminated with oil from conveyor.

Gurvin Singh
Mohali, Punjab, India

A. There are 3 ways to solve crater problem ...
1. increase the pigment content (ash content)
by adding the pigment paste, the pigment will fill the crater, but you must concern the roughness, usually it will increase the roughness value.i think this the most effective way to solve crater for temporary.
2. increase the meQ value ...
by adding the acid, usually organic acid like acetic acid [on eBay or Amazon], it will dilute the oil and reduce the surface tension between the paint and oil. but it will reduce the thickness film, so you must increase the applied voltage to maintain the film thickness, better work on minimum thickness value
3. use the oil adsorbent ...
it will absorb the oil in paint, better use it by turn off the circulation.oil will float on paint surface then use the oil absorbent on it.

For treatment area please check the oil content value on degreasing tank.probably the oil content already high.

Contact your paint supplier and ask about the crater test of fresh paint.

Marga Sbangkit
- Indonesia
August 15, 2009

Q. Dear Sir:
We have conveyor type CED line. Dip time for all baths is 90 secs, but phosphating and ED bath has double dip (2 X 90 secs). We are facing crater issues for past year. That problem suddenly occurs and suddenly disappears, i.e., the problem is not a continuous one -- every 20 hangers once the problem occurs. Sometimes the problem does not occur for 2 - 3 days P)

Jazz Rony
Painting shop Engineer - Chennai, Tamilnadu, India
November 17, 2009

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by Bruggemann & Rach

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A. 1st. check wet ability condition of part or body.
2nd. check oil content of degreasing, purge and make up if oil content has a high value.
3. increase of ash content.
4. usage of oil absorbent
5. check crater oven (use of wet panel difference ED coat another line), cleaning oven if crater check NG.


S Ricardo
- Bekasi, Indonesia
December 11, 2009


Dear Manish,

1)Please check that is crater are coming from fresh paint.
2)Please check the Oil content of the Degreasing Bath
3)Please check the Oven Contamination on the CED coated body
4) Please check the Oil condition on the substrate.

For action you should add the Paste and Acid in the CED bath to increase the Ash & decrease the pH of Bath

Ravi B Sharma
my own - India
July 20, 2010

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