Stripping the Anodic Coating
Question: I have several thousand hose fittings that are a machined casting made of 356-T6 aluminum alloy.
Question:
I have several thousand hose fittings that are a machined casting made of 356-T6 aluminum alloy. The parts are anodized and dyed olive drab. The parts in inventory are no longer needed by our customer so I am looking for a way to remove the anodized color and return the parts to their original, un-anodized appearance. We can then return the parts to inventory to sell as an unanodized commercial grade part. The dimensional tolerance on machined diameters is ±0.005". What do you suggest? C.W.
Answer:
I would suggest making up a stripping bath to the following recipe. This bath will readily remove the oxide coating from the parts without any appreciable affect on the aluminum substrate. The size of the tank used (volume of the bath) may depend on the number of batches you are willing to process in order to get all the parts stripped. It may also depend on what kind of container (tank) you have available. I would suggest anything from 50-250 gal in size. I present the recipe two different ways. Both give the same results, so take your pick.
I would recommend placing the parts to be stripped on a rack or fixture made of aluminum or in a stainless steel basket arranged so that they can't touch each other. Immerse the parts for 1-5 min. Determine the stripping time by running a few test parts first. Be aware that as the bath loads up on aluminum oxide the activity of the bath will decrease. The addition of more phosphoric acid will reactivate the bath. Rinse the parts thoroughly after stripping.
Related Content
-
NADCAP Shop Digitizes to Eliminate Paper Trail
Customizable ERP software has transformed a 27-year-old manual metal finishing job shop into a state-of-the-art paperless company with full digital traceability in about 10 months.
-
Products Finishing Reveals 2024 Qualifying Top Shops
PF reveals the qualifying shops in its annual Top Shops Benchmarking Survey — a program designed to offer shops insights into their overall performance in the industry.
-
Trivalent Chrome Overview
As the finishing industry begins to move away from the use of hexavalent chromium to trivalent chromium, what factors should finishers consider as they make new investments? Mark Schario, chief technology officer for Columbia Chemical offers a helpful overview of this complicated topic.
