ANODIZED - Fort Wayne Anodizing's processes

Automotive Finishing, Spring, 2001 by Beverly A. Graves

At Fort Wayne Anodizing, it's not how it's made.

It's how it's made to last...

Which parts of an automobile benefit from hard coat anodizing? When is it better to anodize? Ft. Wayne Anodizing (Ft. Wayne, IN) has the answers to these and any other questions you may have about anodizing. Just ask William Branstrator, vice president of operations.

"I get a charge out of telling a group of engineers that I can make the surface of aluminum 30-35 points from being as hard as a diamond. You can't cut it with a file. It is about 65-70 Rockwell hard. That is one of the reasons it is used in automotive applications," Mr. Branstrator claimed.

Hard-coated aluminum is non-conductive to electricity to 2,000v. Because the hard coat anodized aluminum is non-conductive, you can bolt it to brass or steel and not worry about generating a galvanic reaction; therefore it is qualified for use in salt/corrosive atmospheres. Typical hard-anodized coatings pass the 1,000 hr 5% salt spray test, ASTM B117. If a duplex seal is applied, the coating has been known to resist corrosion in excess of 50,000 hr.

Mr. Branstrator also compared hard-anodized aluminum to stainless steel. It is less expensive than stainless steel. It machines twice as fast and doesn't weigh as much. This saves on shipping costs. "And it is more durable than hard chromium plating because the coating is integral to the part, not just on the part," explained Mr. Branstrator (see Fig. 1).

"Hot brake fluid is one of the most oxidizing fluids within a car. This fluid could break down most coatings, but not hard anodizing. That is why most ABS brake systems use hard coat anodizing," he continued. Components for ABS brake systems are some of the highest volume jobs Ft. Wayne Anodizing (FWA) runs on its new multi-million dollar hard coat line.

When FWA installed the fully automated, computerized line from Jessup Engineering, it did not have a job ready and waiting. "We did not make any 'widgets' here that we were going to run on it," stated Mr. Branstrator. "We went out and sold the system's capabilities to our customers." And the work came in.

The first job run on the line was for Ford Motor Co. It was a component for a vibration damper on the crankshaft for its 3-liter engine. Ford had opted to use diecast aluminum instead of cast iron to eliminate massive weight on the end of the crankshaft. Although that job is gone due to engineering changes, FWA is now running the vibration damper on the Corvette engine, which is

However, if the Ford engineers return to the original design, FWA would have no problem running it. The advanced computerized program allows pre-programmed job sequences, written up by FWA based on the alloy, surface area to be finished and specifications. The automated system will control tank temperatures and automatically control the drying system. These programmed specifications are stored and may be recalled for future production needs, enabling FWA to maintain exact tolerances... even years later! This automation eliminates human handling once the components are racked, resulting in increased capabilities and greater efficiency in both high-and low-volume production.

The hard coat anodizing line has three hard coating tanks, each with its own self-contained Controlled Power rectifier and cooling system. "If you are fortunate enough to be awarded 100% of an automotive or military job," Mr. Branstrator noted, "you want to be sure you have backup tanks in case something happens. Our customers want to be sure you have the backup in case something happens. Plus, the extra tank increases our capacity by a third and gives us room to grow."

Hard coat anodizing at FWA is accomplished at or just below the freezing point of water. Temperatures are monitored using systems from Process Technology Corp. Conventional (sulfuric) anodizing runs at 70-75F with the rectifier set at 12-17v, depending on the alloy in the tank. During hard coating, the rectifier can be charged up to 100v if necessary because you are building a non-conductive film on the part. "We have to understand what that part is doing at the temperature of an ice cube and then determine what it is going to do in the customer's quality control lab where it is 70-72F," said Mr. Branstrator.

Hard coat anodizing should not be confused with sulfuric anodizing, which places a very thin coating of aluminum oxide on the surface of the aluminum surface. Hard anodizing requires an electrolysis process that produces a dense layer of aluminum oxide both on and in the aluminum surface. The thickness of this hard-anodized coating ranges from 1-3 mil or more. (Thicker coatings may burn, crack or have a powdery appearance.) The coating thickness is a function of current density, time in solution, temperature, the composition of the alloy and the solution itself, which is supplied by SIC Technologies.

Hardness.

Wear characteristics compare favorably with hard tool steel under low loads. Microhardness tests on hard-anodized aluminum typically give values of 500-530VPN. This number refers to the weight required for a diamond indenter to produce an indentation in the coating.