TROUBLE SHOOTN IN CED COATING
• CONTAMINATION (DUST, ION)
• SECONDARY SAGGING
• WATER MARK
• DRY MARK
• BITS FORMATION
• CRATERS * Defect easily happen, IF CED
bath paint Parameters or
• GAS PINHOLE line facilities not monitor
well.
１．Contamination
1) Phenomenon Paint film swells owing
to abnormal deposition.
It is sometimes
accompanied by pinholes. Stick of Alkaline
materials
2) Causes Alkaline materials, for
example degreasing and
phosphate solution drop
Substrate
on the substrate before
ED coating, or ooze from
seams. After ED
Contaminated DI water. coating
ED
3) ①To prevent over spray
Countermeasure to upper portion of
conveyor. Substrate
②To strengthen rinsing
to hunger and box
section of substrate.
Check quality of DI water
Drain permeate
Coagulation
Coagulation.
Coagulation is generally brought about by the addition of
electrolytes like that degreasing or surface chemicals in ED
paint . When an electrolyte is added to in paint solution, the
particles of the solution take up the ions which are oppositely
charged and thus get neutralized. The neutral particles then
start accumulating to form particles of a larger size which settle
down.
Floating Paint lumps
Movement of paint particles &
combined together due to Normal ACED Paint no movement of
Carry over of alkali or acidic chemicals Ions or particles
３．Water mark
1) Phenomenon By baking with water on
paint film, it becomes Water drop
uneven and sometimes ED wet
followed by pinholes. film
2) Causes ①Insufficient setting time
after rinsing before Substrate
baking. Baking
②Water dropping from
hanger, etc. before oven. ED dry
film Unevenness
3) ①Adjust nozzle alignment.
Countermeasure ②To remove water drops
by air blow.
Substrate
２ Sag Marks (ED Drops)
1) Phenomenon Paint solution oozes from
the seams of substrate
during baking and remains
line marks. Seams
In case of high solid
content of the paint
solution, it is easy to swell.
2) Causes ①Weak rinsing to seams.
②Decreasing of UF flow
rate and increasing of solid
Sagging
content of rinse water.
③Increasing of solid
content of bath paint.
3) ①To strengthen rinsing.
Countermeasure ②To maintain UF flow rate.
③To reduce solid content
of bath paint.
POSSIBLE CAUSES OF ED DROPS
➢ UF RINSES NV% HIGH (UF Flux rate low)
➢ IMPROPER WELD SEALER APPLICATION
➢ UF RINSES pH LOW (< 5.0)
➢ BODY SHELL STRUCTURE & DESIGN
➢ LESS FLASH OFF TIME BEFORE ED OVEN
➢ HIGH PRE-HEAT ZONE TEMP. OF ED OVEN.
４．Dry mark
1) Phenomenon Extra paint dries before
rinsing and cannot be removed
by rinsing. Dry mark
2) Causes ①Long time from ED exit to
rinsing.
②Low humidity around ED exit. Normal
film
3) ①To install mist spray within
Countermeasure 30 to 60 seconds after exit
from ED.
②To prevent fall of humidity
by enclosing ED exit area with
vinyl sheet, etc.
5．Craters
1) Phenomenon Because foreign matters, for
example oil put on substrate
before or after ED coating, paint
film makes crater during thermal 【Crater】
flow.
2) Causes ①Oil drops from conveyor. ED
②Oil oozes or spout from seams
during baking.
③Owing to valve and gaskets Substrate 1～3mm diameter
using silicone oil.
④Owing to top coat dust or
silicone materials flying from
Large size.
other process and outside of the
plant.
3) ①To improve oil pan of conveyor
Countermeasure and to prevent excessive
charging of oil to conveyor chain.
②To strengthen degreasing.
③To use oil free valve and
silicone free gasket and to wash
before installation.
④To cover ED coating area with
vinyl sheet, etc. and shut foreign
matters.
7.Gas Pinhole
1) phenomenon Pinhole occurring on
galvanized steel, etc. Gas pinhole
by ED coating. Gas
loophole during ED
coating remains after
baking. It is very small
hole as if it is pushed
by needle.
2) Causes ①Thick Zinc coating.
②High applied voltage. Normal
③Low temperature of film
bath paint.
4. Contamination
3) ①To reduce voltage.
Countermeasure
②To increase bath
paint temperature.→
（℃）
③To increase solvent
content in bath paint
and improve thermal
Dust Issue
Dust is one of the most vexing and challenging problems encountered in the paint shop. It
never seems to end and is often hard to eliminate. Dirt can come from many sources
including some that are not even under the direct control of paint line personnel.
What is dust ?
Dirt is any visible, objectionable object in or under the paint film
Almost every freshly painted surface on a vehicle attracts airborne contaminants; tiny
particles of dust stick to the wet paint and, as it dries, become part of the surface. Despite
their small size, such particles
compromise final quality and may become the source of progressive degradation of the
integrity of the paint finish.
Walls, floors and ceiling • Fans (Ceiling, exhaust and bracket) • Conveyor • Trolleys 2.
People • Skin flakes and oil • Clothing debris (lint, fibers, etc) • Hair 3. Tool Generated •
Brooms, mops and dusters • Friction Particles (Sand paper)
Dirt has three Major sources In Paint
1>Process Process dirt develops within the bath or rinses from inadequate
solubilizer levels, pump shear, altered circulation and improper filtration. In the
early stages, dirt appears on a horizontal surface, but in severe cases it can affect
all surfaces.
2>Environmental dirt is caused by airborne particles that fall into the bath or
settle on the parts. Electro coat areas exposed to vehicular traffic, ventilation fans,
and grinding/sanding operations are susceptible.
3>Oven dirt is caused by condensation of electro coat by-products that flake off
when drying. On a cured part, oven dirt is more surface oriented, while process
and environmental dirt is somewhat imbedded in the paint film.
4>People People are a major source of dirt. Lint and fibers from clothing are the
main culprits. Hair dandruff, Skin can sometimes lead to dirt
Where does dust come from?
It can come from many sources. Here is a partial list:
1.Weld shop
2.Pre-Traetment
3.Paint
4.Sanding
5. Sealers
6. Compressed air
7. Blow-off air
8. Ovens
9.Conveyors
10.Clothes
11.Gloves
12.Hair
13.Plant air
Dust Analysis EPMA (Electron Probe Micro Analyser)
