-- The Home Page of the Finishing Industry

on this site
current topics
Live! From beautiful Pine Beach New Jersey: Welcome to the world's most popular metal finishing website

topic 2050

White/light anodizing on aluminum casting


We are in the telecommunications industry. I am involved in the design of outdoor enclosures. We are currently working on an enclosure approx. 1.5 cubic size manufactured from cast aluminum. We have experimented with different types of coatings to help in the emissivity of the heat generated from the internal components as well as being thermally reflective. White powder coating has worked well but is somewhat expensive. Anodizing is more cost effective, but has proven to be less reflective due to the fact that it turns the aluminum a much darker color. Has any one heard of a white anodizing process or any similar process that might be of use in this situation? I'd appreciate any feedback.

Rick O [last name deleted for privacy by Editor]
communications - Petaluma, California


The gentleman who wrote Letter # 2053 has a problem similar to yours. Many people who design parts made from cast alloys are quite disappointed at the appearance after anodizing. Most common cast alloys are made with silicon as the major alloying element- often in the range of 4 to 23%. The more silicon the worse the situation- this element causes the anodic oxide to turn grey, and since hardly any cast part can solidify all at once in the mold, there is often a striation of the silicon and other alloying elements, causing the grey color to be variegated. This latter situation is especially true on any as-cast surface. Any time aesthetics of a part is important, these facts must be considered. There is no light colored anodize dye with anywhere near the hiding power to hide the mottled effect. Actually black dyes will hide the poor appearance best, unless your casting alloy is one that is highly porous and prone to bleedout. Consider also that a black coating has much higher emissivity than white. Is white necessary?

There is a series of cast alloys, the 500 series, I believe some call almag, with magnesium as the major alloying element instead of silicon. I have seen boat hardware made from one (512?) that retain their silvery aluminum appearance, but I don't know enough about their metallurgy to know why these alloys are not used more- perhaps it's a cost issue.

I still believe that for maximum outdoor corrosion resistance and best appearance that a formed wrought alloy would be best in the long run.

phil johnson
Phil Johnson
- Madison Heights, Michigan

If you have a question in mind which seems off topic, please Search the Site

ADD a Q, A, or Comment on THIS topic START an UNRELATED topicView CURRENT HOT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2019, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.