Cause Analysis
I. Sagging
The main reasons:
1. The film thickness is too thick.
Solutions: during the wet to wet spraying process, it is necessary to leave enough flash-off time, control the film thickness within the standard.
2. The viscosity is too low.
Solution: according to the coating specification control the dilution ratio strictly.
3. The solution evaporation is slow.
Solution: use the special thinner, preheat the substrate and strengthen the ventilation.
4. The substrate roughness is not enough.
Solution: increase the surface roughness of substrate properly.
II. Particle
The reasons
1. The coating has not been filtered.
Solution: please filter the coating with suitable nylon filter or stainless steel still filter.
2. The workplace is unclean.
Solution: keep the polished section far away from the spray room, brush floor coating to avoid dust.
Please keep the workplace clean.
3. The stirring of coating is incompletely.
Solution: rolling the coating by the rolling machine in the speed of 60RPM for 1 hour, or stirring the coating by stick to make sure no sediment in the bottom of barrel.
4. The substrate is unclean.
Solution: washing the substrate with acid and alkali, then rinsing
with water before dry the substrate.
III. Fish eye
The main reasons:
1. The substrate surface is unclean.
Solution: make sure the substrate is clean.
2. The coating is polluted by oil.
Solution: add the oil-water separator.
IV. Orange skin
The reasons:
1. The substrate is too rough.
Solution: keep the roughness in the normal range.
2. The substrate temperature is too high leads to orange skin.
Solution: need to improve the cooling effect.
3. The oil pump capacity and capitalization is too small, the spraying distance is too far or too near.
Solution: adjust the spray gun, meanwhile adjust the distance of spray gun and the workpiece.
4. The viscosity of the coating is too high will lead to orange skin.
Solution: use thinner to adjust the viscosity to the suitable application viscosity.
5. The temperature increased too fast will lead to orange skin.
Solution: adjust the curing temperature or reduce the tunnel’s speed.
V. Bubbles and blister
Main reasons:
1. The solution volatilized too fast.
Solution: adjust the solution.
2. The primer has not been baked.
Solution: reduce the tunnel speed or increase the baking temperature.
3. The viscosity of the coating is too high.
Solution: need to adjust the viscosity by thinner.
4. The coating is directly used after stirring.
Solution: keep the coating for a while until without bubbles or add defoamer.
5. The film temperature is increased too fast
Solution: reduce the tunnel speed.
6. The substrate has bubbles.
Solution: change the substrate.
VI. Substrate reveal
The reasons:
1. The coating coverage capacity is weak.
Solution: increase the pigment quantity.
2. The precipitated pigment of the coating has not been well stirred before use, or the coating has not been well stirred.
Solution：stirring the coating completely.
3. The coating is too thin.
Solution: adding thickener instead of thinner.
4. The film thickness is too thin.
Solution: keep the film thickness within the normal range.
VII. Floating
The main reasons:
1. The film thickness is too high, the upper layer and down layer occurred convention.
Solution: reduce the oil pump capacity.
2. The coating is too thin, and the oil pump capacity is too large.
Solution: do not add thinner.
3. The coating is not well stirring before use.
Solution: stirring the coating completely before use.
VIII. Low gloss
The main reasons:
1. The substrate is too rough.
Solution: reduce the surface roughness of the substrate.
2. The film thickness is too thin, the oil pump capacity is too less.
Solution: increase the oil pump capacity.
3. The workplace is unclean or the curing temperature is too high.
Solution: make sure the workplace is clean. Reduce the curing temperature.
4. The substrate is unpolished.
Solution: polish the substrate after produced.
5. The workpiece temperature is too high before spray the topcoat, so the topcoat is too dry.
Solution: reduce the baking temperature or make sure the workpiece is cooled down before spraying the topcoat.
IX. Crack
The main reasons:
1.The topcoat is too thick.
Solution: reduce the oil pump capacity, reduce the solid content of coating.
2.The substrate temperature is too high before spray the topcoat.
Solution: reduce the baking temperature, enhance the cooling and ventilating.
X. Discoloration
The main reasons:
1.The primer has not been well baked before spray the topcoat.
Solution: increase the baking temperature of the primer, or reduced the tunnel speed.
2.The curing temperature is not enough, or the tunnel speed is too fast.
Solution: increase the curing temperature or reduce the tunnel speed.
3.The coating has not been well stirred.
Solution：stirring the coating evenly and completely.
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