Introduction: Paint discoloration is a common quality issue during storage, referring to the deviation from the initial color state. This article systematically analyzes the causes of discoloration and provides complete solutions covering pigment selection, dispersion process optimization, and packaging improvement.
What is Paint Discoloration?
- Green paint appears blue after opening
- Colored paint separates with clear liquid layer
- Color suspension and floating in compound color paints
- Metallic pigments lose luster, turning green or dark
Common Causes of Paint Discoloration
- Formulation and Compatibility:
- Poor compatibility between resins and pigments
- Large density differences in compound color pigments, lighter ones float, heavier ones sink
- Chemical Reactions:
- Pigment chemical reactions: Iron blue fades due to reduction in insufficient air
- Inter-component reactions: Gold and aluminum powders react with varnish, losing metallic luster
- Container reactions: Shellac varnish and nitrocellulose lacquer darken when reacting with iron containers
- Process and Packaging:
- Moisture incorporation during production
- Insufficient dispersion and grinding time
- Improper packaging container selection
Solutions to Prevent and Fix Paint Discoloration
- Formulation and Process Optimization:
- Add 0.2%-1% wetting and dispersing agents, such as: silicone oil, polyacrylates, polymeric polycarboxylates, polyaminoamide phosphates, fatty alcohol sulfates
- Avoid moisture incorporation, appropriately extend dispersion and grinding time
- For metallic pigment paints, use neutral paints and add metallic pigments at the final stage
- Packaging Improvement:
- Use galvanized or tin-plated iron drums
- Package special paints (shellac varnish, nitrocellulose lacquer) in plastic drums, porcelain jars or glass bottles
- Separate packaging for metallic pigments and paints, mix before use
- Problem Identification:
- Compound color paints returning to uniform color after thorough stirring are not true discoloration
- Color restoration after air exposure is normal phenomenon
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