Analysis of the performance of aluminum alloy cabinet handles with different surface treatment processes in humid environments

（1） The core challenge of the wet environment to the handle
Typical hazards of humid environments (e.g., kitchens, bathrooms) include:
Water vapor permeation: long-term high humidity (RH>70%) leads to metal oxidation;
Chemical corrosion: soapy water, detergents (pH fluctuations) accelerate the decomposition of the coating;
Microbial influences: Mold grows in the crevices and disrupts coating adhesion.

（2） Comparison of the performance of mainstream processes in humid environments
1. Anodizing
Moisture Resistance Mechanism:
The oxide film (Al₂O₃) forms an integral part with the aluminum matrix, and the porosity is about 15-20%, and it is difficult for water vapor to penetrate after sealing treatment.
Measured performance:
Salt spray test (ASTM B117): no white rust (aluminum oxidation) for 500-1000 hours, fine spots locally after 1000 hours;
Water resistance: soaked in boiling water for 24 hours, the oxide film does not swell and fall off;
Detergent resistance: 5% soapy water 500 times with no change in color.
Failure Modes:
After the oxide film is worn out in long-term friction parts (such as the grip of the handle), the aluminum matrix is easy to rust when it comes into direct contact with water vapor.

2. Powder Coating
Moisture Resistance Mechanism:
The 100-150μm thick thermoset powder coating forms a physical barrier against water vapor and the aluminum matrix.
Measured performance:
Salt spray test: 1000-2000 hours without corrosion, coating without bubbling;
Water resistance: After 72 hours of immersion, the adhesion of the coating (100 grid test) still reaches class 0;
Acid and alkali resistance: 5% citric acid/sodium hydroxide solution wiped 200 times, the coating has no fading and cracking.
Failure Modes:
If there is a slight damage to the edge of the coating (e.g. bumps during installation), water vapor can easily penetrate the aluminum base from the damage, resulting in "bottom corrosion".

3. Electroplating
Moisture Resistance Mechanism:
Metal plating (e.g. chromium/nickel) acts as a barrier, but the electrochemical potential difference between aluminum and the plating can easily form corrosive cells.
Measured performance:
Three-layer electroplating (copper, nickel, chromium): salt spray test for 500-800 hours without corrosion, single layer nickel plating only resists 200 hours;
Water resistance: After 100 hours of immersion at room temperature, "white rust" (aluminum oxidation) begins to appear on the edge of the coating;
Scratch resistance: The chromium coating has high hardness, but the water vapor penetrates into the micro-cracks of the coating layer, which is easy to cause the aluminum matrix to expand and the coating to peel off.
Failure Modes:
The coating has a high porosity (about 5-10%), and the water vapor permeates to form a "down-erosion", which appears to be a bulging coating.

4. Electrophoretic Coating
Moisture Resistance Mechanism:
The water-soluble resin coating is homogeneous and dense (20-30μm thick) and seals the aluminum surface at the molecular level.
Measured performance:
Salt spray test: no corrosion for more than 1000 hours, passed ASTM B117 strict rating;
Humidity and heat resistance: 30 days of storage at 80°C/95% RH, no discoloration or peeling of the coating;
Resistant to detergents: 10% oil cleaner repeatedly wiped, coating gloss retention rate > 90%.
Failure Modes:
Coatings can saponify and decompose under extreme conditions, such as long-term exposure to concentrated acids, but perform well in daily wet environments.

(3) Process selection strategies for special wet scenarios
1. Kitchen environment (oil smoke and water vapor mixture)
Preferred Solution:
Powder coating (oil-resistant cleaner, coating is easy to wipe);
Anodizing (anti-oil smoke adsorption, non-staining oxide film).
Pit avoidance tips: avoid electroplating parts, oil smoke infiltrates into the pores of the coating layer and is difficult to clean, accelerating corrosion.
2. Bathroom environment (soapy water, high temperature steam)
Core Requirements:
Alkali resistance (soapy water pH≈9-10) High temperature steam resistance (above 50°C).
Top Alternative:
Electrophoretic coating (excellent alkali resistance, the coating does not soften in high-temperature steam);
Hard anodizing (film thickness≥ 25 μm, scratch resistant and resistant to temperature differences).
3. Coastal environment with high salt spray
Extreme Protection Schemes:
Anodizing fluorocarbon spraying composite treatment (first oxidizing to form a substrate, and then spraying 0.05mm fluorocarbon coating), salt spray test can withstand more than 3000 hours; Electrophoretic coating Nano ceramic sealing layer (SiO₂ protective layer is formed on the surface of the coating, and the hydrophobicity is increased by 90%).

(4) Guidelines for the use and maintenance of humid environments
Daily maintenance:
Wipe the handle with a soft cloth dipped in water every week to remove moisture and stains on the surface;
Plated parts need to be coated with metal anti-rust oil (e.g., WD-40) once a month to fill in the micro-cracks in the plating.
Emergency Troubleshooting:
When the coating is damaged, immediately apply the damaged area with transparent nail polish to temporarily isolate moisture;
If there is a slight white rust on the anodized parts, you can wipe it with a 10% citric acid solution, rinse it with water, and then wipe it dry.
Life Cycle Management:
Electrophoretic Coating / Powder Coating Handles: Check coating adhesion every 5 years and reapply if necessary;
Anodizing handle: more than 10 years need to pay attention to the wear of the oxide film, and it can be re-oxidized when the wear is serious.

(5) The ultimate purchase advice
The first choice for cost performance: powder coating (taking into account moisture resistance and color richness, suitable for 90% of home kitchens/bathrooms);
Extreme environment just needs: electrophoretic coating (medical-grade moisture-proof, suitable for coastal areas or long-term high humidity environments);
Retro-style compromise: three-layer electroplating sealing glaze (while ensuring the metallic luster, reducing water vapor penetration through the sealing glaze).