【Anodizing Q&A】
Q: What’s the difference between regular anodizing and hard anodizing?
A: Thickness and hardness: Regular anodizing is 5-20 microns thick with double the original hardness, while hard anodizing forms a 60-200 micron layer with triple the original hardness. Hard anodizing tends to yield a yellowish hue. Color: Regular anodizing offers a wider color range than hard anodizing.
Q: What causes color variation in anodizing?
A: Various factors contribute, including differences in oxidation batches and uneven material composition. Large parts and concentrated contact points in fixtures can also result in varying oxidation levels.
Q: How to rectify undesirable colors after anodizing?
A: Rectification typically involves deoxidization, which removes the oxide layer for re-anodizing. However, repeated rectifications can lead to dimensional changes and increased deviations.
Q: What distinguishes anodizing from passivation on aluminum?
A: Both processes form protective layers, but anodizing creates a thicker layer through electrolysis, resulting in non-conductive surfaces, whereas passivation forms a thinner layer via chemical oxidation, allowing for conductivity.
Q: Issues and solutions for anodizing aluminum with blind holes?
A: Blind holes pose challenges as acid residue may cause uneven oxidation during coloring. Solutions include plug use, ultrasonic water removal, and hook adjustments, but design modifications to avoid blind holes are optimal.
Q: What colors can be achieved through anodizing?
A: Except for white and off-white (due to pigment molecular size), nearly all Pantone colors can be matched. White finishes may require post-anodizing painting for optimal aesthetics and durability.
Q: Which is more wear-resistant, brushing or sandblasting?
A: It depends on the thickness of the oxide layer. While sandblasting may appear more resistant due to fewer visible scratches, both techniques remove stresses, with sandblasting offering finer surface finishes.
Q: Does sandblasting cause workpiece deformation?
A: Yes, especially in thin workpieces. Adjustments in air pressure, nozzle angle, or using fixtures for uniform blasting can mitigate deformation.
Q: What sandblasting grit is needed to conceal tool marks?
A: Finer grit results in smoother surfaces but may obscure tool marks less. Consultation with machining and anodizing facilities is advised.
Q: Can die-cast aluminum undergo anodizing?
A: While silicon content in die-cast aluminum can hinder anodizing and lead to discoloration, some facilities offer solutions. Consultation with manufacturers is recommended.
Q: What causes material lines after anodizing aluminum?
A: Seamless aluminum tubes or welded plates exhibit distinct patterns due to different metallographic structures, challenging to address. Diminished brightness and opting for darker colors may reduce visibility.
Q: How to prevent fingerprint absorption post-anodizing aluminum?
A: Ensure thorough sealing to close oxide pores, preventing oil adhesion to the honeycomb-like oxide layer.
Q: Can dual-color anodizing be achieved?
A: Yes, through multi-stage anodizing processes involving machining for secondary oxidation.
Q: Can aluminum parts with embedded metals be directly anodized?
A: It’s not advisable due to potential corrosion from long-term exposure to acidic solutions. Pre-anodizing embedding or using identical materials for embedding is recommended.
Q: Why do aluminum parts fade after outdoor exposure post-anodizing?
A: Exposure to UV rays accelerates fuel aging and decomposition, causing fading. Utilizing UV-resistant coloring agents is advisable for outdoor applications.
