The National Association for Surface Finishing
Aluminum wheels show how surface finishing makes everything a little cooler.

Aluminum Finishing

The course consists of 10 lessons. Students successfully completing the exam will be given credit towards the AESF Foundation Master Surface Finisher (MSF) certification.

Course Options

Intended Audience

This training program is designed to be beneficial for employees and supervisors working in both captive and job shops performing anodizing and other finishes on aluminum. Trainees should have at minimum a high school diploma. Some experience in processing parts for surface finishing is helpful but not required. The training materials and instruction are in English. In many cases, metric and/or US/English units of measurement are utilized. Students are taught how to convert between the two systems of measurement.

Goal

The goal of this course is to provide the student with a broad range of information related to metal finishing operations that are commonly conducted on aluminum.

Part-1

1. The Metallurgy of Aluminum
This lesson presents the basic properties of aluminum along with a description of the major methods used to produce parts from aluminum, including their impact on finishing. Students will learn about forging, die casting, stamping, extruding and drawing of aluminum. Also covered is the subject of alloying elements and their impact on the surface finish after anodizing. The differences between 1000, 2000, 3000, 4000, 5000, 6000 and 7000 series alloys are detailed.
2. Mechanical Finishing of Aluminum
This lesson covers mechanical means of finishing aluminum parts, including grinding, polishing, buffing, vibratory finishing, shot peening and blasting. The differences between various polishing compounds/media are provided along with a basic understanding of the differences between polishing hardware.
3. Preparing Aluminum for Anodizing and Plating
This lesson details the steps utilized to prepare aluminum for anodizing or chem film (chromate) conversion coating. Cleaning via ultrasonic, chemical soak, and electrocleaning methods are discussed. Special attention is given to the use of deoxidizing solutions and various acid dip mixtures. Newer technologies such as the use of biological cleaners are also provided. A significant amount of material on the zincate process for plating on aluminum is included in this lesson.
4. Aluminum Bright Dips and Electropolishing
This lesson covers the various solutions/methods that can be used to brighten the surface of aluminum prior to finishing. Included is a discussion of electropolishing equipment and phosphoric-sulfuric electropolishing solutions. The section on bright dipping covers equipment solutions and trouble-shooting of the processes.
5. Etching and Chemical Milling of Aluminum
In this lesson, the student will be provided with a discussion of the various methods of etching and chemical milling of aluminum using alkaline and acidic solutions, with emphasis on etching and chemical milling using sodium hydroxide. Operational conditions that affect etching/milling rates and ultimate dimensions of the parts are provided. The hazardous nature of the etching process is discussed with an example of a hydrogen explosion related to an etching process at a European anodizing facility.
6. Equipment Requirements for Anodizing
This lesson covers design issues related to the individual components of an anodizing process, including tanks, rectification, cathodes, filtration, racking, agitation systems, and process ventilation. A brief discussion of coil anodizing and brush anodizing is also provided.
7. Sulfuric Acid Anodizing of Aluminum
This lesson covers the MIL-A 8625 Type II anodizing process. Solution make-up and operational conditions including the role of impurities are discussed in detail. Common problems with the process and possible solutions are also provided. A brief discussion on methods used to measure/monitor anodic thickness/weight of coating is also covered. A section on “keys to successful bright anodizing” may be of special use to decorative anodizing facilities.
8. Coloring and Sealing of Anodized Aluminum
This lesson provides guidance for coloring anodic coatings using immersion dye, electrolytic methods and integral (two step) color anodizing. Operational conditions for obtaining the best results are provided as well as a discussion of the merits of each technique. The lesson also provides descriptions of the most popular methods of sealing anodic coatings, including nickel acetate, hot water and dichromate sealing along with more recent developments such as low temperature sealing and two step sealing. A discussion of seal quality tests is also provided.

Decorative anodizers will find the “keys to successful dyeing” and “keys to successful nickel salt sealing” sections very useful in focusing on the most important operational variables in a dye tank.
9. Hardcoat & Alternate Anodizing Solutions
This lesson will detail the most commonly employed methods of obtaining MIL-A 8625 Type III coatings. Included are the Martin, MAE, Hardas, Sanford and Metalast hard coating processes. A discussion of operational parameters affecting wear resistance is provided. The Taber Abrasion resistance test is also discussed along with a brief discussion of alternate hardcoat anodizing solutions.
10. Anodizing Aluminum in Chromic Acid and Alternate Solutions
This lesson details the MIL-A 8625 Type I (chromic acid), Ic (sulfuric-boric acid) and IIb (thin film sulfuric acid) anodizing processes. Solution make-up, operational conditions and a discussion of the role of impurities is included, along with the different results obtained from various alloys.
11. Conversion Coatings on Aluminum
This lesson will provides operational and troubleshooting guidance for processes that produce chromate type (Alodine® and Iridite®) films on aluminum. Solution make-up and operational conditions for maximizing results are provided. Discussions of causes of salt spray failures, European WEEE and RoHS initiatives and available non-chromated conversion coatings are also given.