12.13.3 Diagnostic Information and Procedures
12.13.3.1 Common Paint Defects and Treatment

Note

Adding black box in the table indicates the treatment.

Defects

Causes

Treatment

Powder

1. Film subject to strong erosions, such as

the strong ultraviolet radiation.

2. Incorrect ratio in the paint mixture.

3. Coating low resistance to sun and bad

weather.

4. Vehicle  is  not  cleaned  regularly  or

thoroughly.

5. Incorrect choice of car cleaning agents

or polishing wax too coarse.

1. Polishing

2. Conventional grinding and polishing

3. Deep grinding and finesse polishing

4. Local paint repair

Plastic Paint Peeling

1. Poor adhesion between the coating and

the substrate or outer coating too hard

2. Coating too thick or erosion caused by

water vapor, acid and alkali in the air

3. Under  coating  treated  incorrectly;

pinholes  and  defects  in  the  outer  paint
layer

1. Polishing

2. Conventional grinding and polishing

3. Deep grinding and finesse polishing

4. Local paint repair

Cracking

1. Primer inadequately stirred

2. Spray paint too thick

3. Middle coating too thick

1. Polishing

2. Conventional grinding and polishing

3. Deep grinding and finesse polishing

4. Local paint repair

Bird Droppings

Erosion

1. Bird droppings erosion

1. Polishing (mild erosion)

2. Conventional grinding and polishing (medium erosion)

3. Deep grinding and finesse polishing

4. Local paint repair (severe erosion)

Scratch

1. Film with low hardness

2. Hard objects scratch

1. Polishing (minor scratches)

2. Conventional grinding and polishing (thick scarring)

3. Deep grinding and finesse polishing

4. Local paint repair (scratched)

Body, Sheet Metal and Painting

Paint/Coatings

12-161

Defects

Causes

Treatment

Corrosion

1. Thin film edges

2. Corrosion at minor collided areas

3. Acid and alkali erosion

1. Polishing

2. Conventional grinding and polishing

3. Deep grinding and finesse polishing

4. Local  paint  repair  (serious  rusted  metals  need  to  be

repaired before painting)

Paint Peeling

1. Poor adhesion between the coating and

the substrate or outer coating too hard

2. Coating too thick or erosion caused by

water vapor, acid and alkali in the air

3. Under coating treated incorrectly

4. Pinholes and defects in the outer paint

layer

1. Polishing

2. Conventional grinding and polishing

3. Deep grinding and finesse polishing

4. Local  paint  repair  (serious  rusted  metals  need  to  be

repaired before painting)

Acid Rain Erosion

1. Acid rain erosion

1. Polishing (mild erosion)

2. Conventional grinding and polishing (medium erosion)

3. Deep grinding and finesse polishing

4. Local paint repair (severe erosion)

Gloss

1. Film eroded by the acid, alkali, electric

arc,  sea  water  and  other  strong
corrosive salty spray

2. Incorrect maintenance methods in harsh

conditions

3. Poor paint durability

4. Incorrect  paint  mixture  ratio,  paint

durability deterioration

1. Polishing (mild loss of light)

2. Conventional  grinding  and  polishing  (moderate  loss  of

light)

3. Deep grinding and finesse polishing

4. Local paint repair (severe loss of light)

Bubbling

1. Film exposed to a humid environment for

a long; water vapor infiltration into paint
film;  water  and  gas  bubbling  when
temperature rises

2. Corrosion caused by infiltrated materials

3. Fuel, acid, alkali and other erosion

1. Polishing

2. Conventional grinding and polishing

3. Deep grinding and finesse polishing

4. Local  paint  repair  (serious  rusted  metals  need  to  be

repaired before painting)

12-162

Paint/Coatings

Body, Sheet Metal and Painting

12.13.4 Removal and Installation
12.13.4.1  Common  Coating  Film  Defect
Treatment Example

FE12-1045b

1.

Before  polishing,  clean  the  surface  with  de-greasing
materials.

FE12-1046b

2.

Firstly fully soak a sponge and squeeze excessive water.

3.

Apply a small amount of polishing wax to the surface and
adjust the polishing machine speed.

FE12-1047b

4.

Put the sponge onto the surface, turn on the machine with
a speed at 2,500-3,000 r/min. Gently press the sponge to
polish for 3-5 s.

Note

During  operation,  keep  the  machine  stable  and
move  gently.  Do  not  work  too  long  to  avoid
overheating,  as  the  paint  will  be  damaged  by  the
heat.

5.

Use a cleaning cloth to wipe the excessive wax.

Body, Sheet Metal and Painting

Paint/Coatings

12-163

12.13.4.2  Conventional  Grind  and  Polishing
Treatment Example

FE12-1048b

1.

Before  polishing,  clean  the  surface  with  de  greasing
materials.

FE12-1049b

2.

Apply a small amount of polishing wax to the surface and
adjust the polishing machine speed.

FE12-1050b

3.

Put the wool ball onto the surface, turn on the machine
with a speed at 2,500-3,000 r/ min.

Note

During  operation,  keep  the  machine  stable  and
move  gently.  Do  not  polish  too  long.  Keep  the
polishing  time  as  short  as  possible,  the  polishing
area as small as possible.

4.

Firstly fully soak a sponge and squeeze excessive water.
Apply a small amount of polishing wax to the surface. Put
the sponge onto the surface, turn on the machine with a
speed at 2,500-3,000 r/min. Gently press the sponge to
polish for 3-5 s.

Note

During  operation,  keep  the  machine  stable  and
move  gently.  Do  not  work  too  long  to  avoid

12-164

Paint/Coatings

Body, Sheet Metal and Painting