Preparing your metal for finishing 

Common answers to reduce material waste

One of the main goals of a fabricator and the finisher is to ensure they get a quality product, done right the first time. There are several steps a fabricator should take to ensure a successful run of their material. The most successful thing a fabricator can do is form a good working relationship with their finisher. Some important points to consider are:

• Consistency in aluminum. The easiest way to ensure consistency in your aluminum parts is to get your material from one metal source.
• Do not mix alloys of aluminum. Mixed alloys or even tempers will not produce uniform results. For best results use 6063 alloys for extrusions and 5005 for sheet stock.
• Perform as much bending and forming as possible prior to finishing. Anodic films are very hard. In fact on a gemological scale (1-10, where a diamond is a 10) an anodic film is rated a 9, similar to that of a sapphire. As a result most post-production bending will lead to the film “crazing” which will give the appearance of a spider web. Crazing causes a series of small cracks in the finish.
• Storage of material. Store aluminum in a dry and controlled environment. Do not allow moisture to build-up between the pieces as this will cause severe corrosion (white rust) that will not be removed in the finishing process. Not only is this important to the fabricator, but it is equally important that the finisher ensure proper climate control where aluminum is stored.
• Avoid tape or adhesives on material. Tape or adhesive on the aluminum may leave a residue that may not be removed in the anodize process.
• It is important to discuss with your finisher the specification desired. TIN the architectural industry, the most recognized specification is  AAMA 611-98. If specific parameters are required it is important to furnish the finisher with the desired requirements to ensure the job is completed to the customers expectations.
• Welded parts will show a color difference on the weld versus the rest of the part. The heat developed from the welding process can disturb the metallurgy on nearby metal and cause a localized discoloration after anodizing. As a fabricator ensure the proper alloy welding wire is used (5356 alloy), and the lowest possible heat.
• Proper drainage holes are essential to prevent solution entrapment. Holes are essential for drainage of solution allowing entrapped gas to escape from the parts. Welded joints will still cause anodize chemicals to weep out.
• The finisher needs to know where parts can be racked. There are a variety of ways anodizers can rack your parts, welding customer material to spline bars to  using a screw down bolt system. In either case contact marks are visible on the aluminum. It is important to define what is acceptable and what is unacceptable with regards to exposed surfaces and rack marks.
• Good shipping practices are essential to a quality job. The fabricator should package metal carefully prior to shipment to the finisher to ensure the metal arrives dry and free of scratches and dents.

Metal free from defects will produce a higher quality finish.  Avoid sending your finisher metal with scratches, dings, heavy die lines, die pick-up, etc. Metal quality defects will show through the anodize process. On a positive note, the anodize process will mask some metal defects. The etch process will moderately and even in some cases remove small scratches, nicks and die lines. As a rule of thumb if you run your fingernail across the defect and can noticeably feel the defect it will not be removed in the anodize process.