What aluminum alloys are recommended for anodizing?
Most aluminum alloys will build aluminum oxide in an anodizing tank, so the answer to this question depends on the anodizing process and the desired result.
- Copper containing 2000 series are generally the most difficult to anodize and 5000 or 6000 series are the easiest.
- SAF recommends 5005 aluminum alloy for sheet 6063 aluminum alloy for extrusion.
This chart from the Aluminum Anodizers Council is a useful guide.
|Aluminum Alloy Series (AA)*||Alloying Constituents||Metal Properties||Anodized Coating Properties||Uses||A.Q.** Types||Non-A.Q.** Types||Aluminum Alloy Finishing Advice|
|1XXX||none||soft, conductive||clear, bright||cans, architectural||none||1100, 1175||Care should be taken when racking this soft material good for bright coatings susceptible to etch, staining|
|2XXX||Copper||very strong, hard, low elongation||yellow, poor protection||aircraft, mechanical||none||2011, 2017, 2219, 2224||Since copper content is >2%, these produce yellow, poor weather-resistant coatings. Don’t mix with other alloys on load|
|3XXX||Manganese||strong, small grain||grayish-brown||cans, architectural, lighting||none||3003, 3004||Difficult to match sheet-to-sheet (varying degrees of gray / brown). Used extensively for architectural painted products|
|4XXX||Silicon||strong, fluid||dark gray||architectural, lighting||none||4043, 4343||Produces heavy black smut which is hard to remove 4043 & 4343 used for architectural dark gray finishes in past years|
|5XXX||Magnesium||strong, ductile, fluid||clear, good protection||architectural, welding wire, lighting||5005, 5657||5052, 5252||for 5005 – keep silicon <0.1% and magnesium between 0.7% and 0.9%, maximum of +/- 20% for job watch for oxide streaks|
|6XXX||Magnesium & Silicon||strong, ductile||clear, good protection||architectural, structural||6063, 6463||6061, 6101||Matte – iron >0.2%, bright – iron <0.1%, 6063 best match for 5005, 6463 best for chemical brightening|
|7XXX||Zinc||very strong||clear, good protection||automotive||none||7029, 7046, 7075||Zinc over 5% will produce brown, tinted coatings, watch zinc in effluent stream, good for bright coatings|
Source: Aluminum Anodizers Council (AAC) Technical Bulletin #2-94, Aluminum Alloy Reference for Anodizing