Anodizing is an electrochemical process that creates a decorative and durable coating on aluminum. The process contains multiple variables that are complex and do require an understanding and commitment to best practices and risk management. The difficult challenge for any anodizer is first making sure that the goals and expectations of the manufacturer are understood. Metal finishing is that final step in the supply chain before delivery of a finished good which requires the utmost in attention to detail.
There are things that anodizing can do, and there are things that anodizing cannot do. When we hear customers say “don’t you just dip it?” related to the anodizing process it brings up all sorts of red flags for us. It is easy to “blame the anodizer” when things go wrong in the process. In the 40 years that Alpha Metal Finishing has served the manufacturing industry we have found many critical factors involved from beginning to end in providing consistent, high quality results in anodizing. Here are just five of the top factors that we feel impact quality:
1. Source Material
The aluminum alloy itself can determine the final result of the anodizing finish in many ways. Each alloy has a different composition of alloying elements, some of which anodize very well and others not so much. For example, 6061 aluminum is one of the most popular alloys chosen by machine shops and manufacturers for its strength, surface finish, corrosion resistance to atmospheric conditions and its workability.
After choosing the appropriate alloy, it is important to use the same lot if possible throughout the job. There can be variations in the stock from the supplier. The quality of the stock (primary vs. secondary) from the supplier as well as how it was forged or extruded can have a significant impact on the final result of the finish after anodizing. For more information on alloys suitable for anodizing we recommend visiting the Aluminum Anodizers Council website at http://www.anodizing.org/?page=alloys.
2. Surface Preparation
Anodizing is unlike any other finishing process in that it reveals the substrate of the aluminum during processing, much like film development. For this reason it is very important to consider every aspect of the surface preparation of the aluminum prior to being sent for anodizing. Proper handling and care of the aluminum parts on the machine shop floor will ensure consistent results in the anodizing process. Alpha has created an excellent resource for how to prepare the aluminum parts at: http://www.alphametal.com/resources/important-tips-prior-to-anodizing.
3. Chemistry Is Critical
One of the most critical components to creating quality, consistent results in anodizing is maintaining tight controls on the chemistry of each bath. There are multiple steps to the process of anodizing which include: cleaning, pre-treatment (etch), anodizing, coloring (except for clear), sealing, and of course there are multiple rinses in between each of these steps.
The controls that must be maintained in each of the steps are: PH, concentration, temperature, as well as time. Chemical suppliers do recommend a range of parameters for each chemical but it is important for each anodizer to do their own research and testing to find an optimal range. This can be done with the assistance of chemical management software as well as consulting with the chemical supplier.
4. Anodizing Tank Controls
The actual step of anodizing requires maintaining multiple controls of the tank itself in order to ensure a consistent, quality coating. Aside from the chemistry of the tank (already mentioned) it is critical to calibrate the electrical source (rectifier) on a regular schedule.
Anodizing time, temperature, agitation and quality of cathodes in the tank also come into play and can impact the final result of the coating on parts during the anodizing process.
5. People Who Care
It would seem obvious that a measure of success in anodizing requires people who are not only competent and knowledgeable but also care about what they are doing. However, in our experience it is painfully surprising to find that many companies do not recognize that their culture is creating the less than desirable results that they are encountering. Principle #5 of The Toyota Way states: “Build a culture of stopping to fix problems, to get quality right the first time.” Principle #12 also applies: “Go and see for yourself to thoroughly understand the situation.” –The Toyota Way, Jeffrey Liker
At Alpha Metal Finishing, we strive to build a culture of people who care and want to create a remarkable experience. We do our best to build relational partnerships as opposed to just transactional ones. Some of the key things to review with a potential anodizer (and really any supplier) are:
Again, there are many details and variables involved in producing high quality anodizing but these are some of primary ones that will help avoid unnecessary reworks or frustration on both sides. When things go right in the anodizing process everyone wins. When things go wrong, finger pointing is easy and rather common. Having a focus on problem solving and a willingness to learn is the key to producing high quality results that make both suppliers and customers happy. For more information on understanding and specifying anodizing we recommend the following resource from Joseph Osborn at OMW Corporation: http://www.omwcorp.com/wp-content/uploads/2018/02/Understanding-and-Specifying-Anodizing.pdf.