Copyright 2009 Eastern Plating Company Website Design by Graphical Media Services General Info PITTING PROBLEMS AND ANODIZING Pitting Prior To Anodizing SUBJECT: Parts being received with pits. PROBLEM: Pitting – Lately we have been receiving parts from our customers with pits. Pits in aluminum are caused by moisture residing on the parts. The moisture can come from several sources – Parts not dried immediately and completely and/or parts exposed to humid air. Although all aluminum is susceptible to pitting some alloys such as 2000 and 7000 series are more susceptible. After researching this problem there is no way to guarantee that pits can be anodized. Pits that do appear to cover with anodize can appear later in the life of the part! THE ONLY WAY TO ANODIZE PARTS WITH PITS IS TO HAVE THE PITS MECHANICALLY REMOVED! PREVENTIVE ACTION: 1. Inspect all material for pits before shipping out for anodizing. A sample lot inspection should be sufficient. 2. Do not allow coolant to sit on parts. Do not allow coolant to dry on parts. Make sure parts are dried immediately and completely after each operation in you process. 3. For synthetic coolants, use the manufacturers mix recommendation for 7000 series aluminum for all materials. This will cover your worse case scenario. Do not over dilute coolant! Talk to your coolant supplier to obtain the proper coolant. 4. Summertime humidity is hazardous to your parts. Ship parts to and from the anodizes in covered containers. BARE SPOTS IN ANODIZE Finding bare spots after anodize and what you can do to help prevent them. SUBJECT: Parts showing bare spots after anodize. PROBLEM: Bare spots in anodize – Although there are numerous reasons for bare spots one of the ones that seem to repeat itself time and time again is foreign substances not removed during normal cleaning processes. Some sticky, oily, and greasy substances will not come off during the normal clean, etch, and deoxidizing process. Foreign substances like these will inhibit the surface from anodizing and dying and will show up as bare spots when completed. This normally requires a undesirable strip and re-anodize and can lead to parts with close tolerances being scrapped. PREVENTIVE ACTION: 1. Recognize the undesirables in your manufacturing processes such as waxes, heavy oils, lubricants, sticky tape, adhesives, etc and eliminate as many as possible. 2. Clean your parts in an industrial part washer or hand wash using an alcohol based cleaner, MEK, or a similar cleaning compound. 3. Do not use masking tape to bundle your parts when shipping them out for plating. This is probably one of the biggest culprits for bare spots caused by contaminated surfaces. 4. After cleaning parts handle with clean gloves or at least clean hands. Believe it or not, we have had parts covered in potato chip oil and this is one of the oils that can leave a residue even after the pre-anodize cleaning process.