Coil Anodizing Guidelines

These guidelines apply to all anodizers regardless of capability.  Most of these are situational so please call us for an explanation if you have any questions.  More will tips will be added based on user feedback.

  1. Always check alloy to be sure it’s anodizing quality.  Mixed alloys or tempers will not produce uniform results.  Die castings are difficult to anodize because of their porous nature, even if they are made from anodizing quality alloy.  We recommend anodizing 5005 for sheet and 6063 for extrusions for best results.
  2. Assemblies must have drainage holes to prevent solution entrapment.  Top holes are required for admission of air, and bottom holes are required for drainage.  Anodizing chemicals can leak through even the tightest welded joints.
  3. Two flat surfaces fastened to one another can trap anodizing solutions and leak out later causing damage to the finish.
  4. Assemblies to be anodized should never include non-aluminum materials.
  5. Be sure to use the correct alloy when welding is involved.  4043 is the worst choice because it will turn a smutty black.  The preferred alloy is 5356.
  6. Anodizing surface quality is dependent on the metal we start with.  Anodizing does not cover up scratches or water stains.
  7. Aluminum must be kept dry and handled with gloves to prevent stains.  It is critical that aluminum be kept dry in transit.
  8. Because the aluminum must carry a certain amount of current per square foot of anodized area, full size sheets must be at least 0.032″ thick.  Formed sheet should also be at least 0.032″ thick.
  9. If you have a specification please provide it on the front-end.  It is always helpful, and usually  critically important, for the anodizer to know about the end-use of the aluminum.
  10. Perhaps most importantly the anodizer needs to know where to rack the material.  The racking points carry the current needed for the anodizing process, but no anodization will occur where the rack touches the metal.  For architectural parts we often use a 3/8″ bolt for racking that has a halo of perhaps a square inch.  Racking instructions are critical!  It is also important to know which surface areas are exposed so we can inspect them for scratches, stains, etc.
  11. Fabrication should be done prior to anodizing.  An anodized surface will crack or craze when formed.
  12. Make sure material is packaged well before shipment to the anodizer.  When possible we will re-use our customers packaging to reduce waste, but our motivation is really to ensure the metal arrives dry and free of scratches and dents.