Why We Need to Know About the Alloy and Its Temper When Anodizing Aluminum
With over 30 commonly available aluminum alloys, and a multitude of tempers for each alloy, this question frequently arises: how important are the roles of alloy and temper in the aluminum anodizing process? The short answer is: VERY important. Let’s familiarize ourselves with some background information so we can answer the question in detail.
Each wrought alloy has a different composition of aluminum with other elemental metals, but it is only the aluminum that anodizes. Temper is determined by the heat treatment and/or methods used to process the metal, and it measures hardness.
What’s the Difference?
Because of the differing constituents, concentrations, and metal structures of alloys, anodizing different alloys and different tempers of the same alloy produce different anodizing results. Results can and do vary by coating color, rate of anodic coating formation, pore size, and susceptibility to certain quality problems—such as burning, softer coatings, and blistering. The appearance of the resulting finish will often appear different, even if both are produced to the same quality standard and under the same process conditions.
A Case in Point
Variations within these factors can lead to poor quality. A few years back, one of our customers sent us a molding for hard coat anodizing to be used to produce downhill skis. A section of the mold quickly started to burn when processed. The question arose: what changed?
A joint investigation identified that while the alloy remained the same, the temper had been altered because the heat-treater did not calibrate his oven, which was significantly out of control. With a major difference in temper, the hard coat anodizing process took a very different turn. Controlling these factors allows us to minimize variation in the metal finish and produce a consistently high-quality finish. Therefore, at DCHN, we always ask our customers to supply the alloy and its temper so we can use this information to deliver great results when anodizing aluminum.
At DCHN, we know that many questions arise when considering aluminum anodizing, hardcoat, and other metal finishing jobs. Our white paper, “12 Proven Tips to Save Time & Money for Aluminum Anodizing, Hardcoat, and Other Metal Finishing Services,” is a guide full of great tips to help you save time and money. Download it now.