[ianking]

First, great site. I have spent time searching and have read the sticky threads, but now I have a few questions that I hope can be answered.

1. If an anodized finish is dyed it must be Type II as Type III is very difficult to dye due to smaller cell size/higher density of cells.

2. Type II is not as hard as Type III.

3. The hardness that is being measured is using Moh's relative hardness scale.

4. The effectiveness of anodizing is directly related to the Aluminum alloy that is used.

I have an instance where I am looking at two sets of aluminum tubes of different alloys. One is anodized the other is a powdercoated with an epoxy/polyester hybrid. By banging each set of tubes together it appears that the powdercoating flexes and indents without cracking or peeling with no apparent change in coloration. The anodized finish also does not appear to crack or peel, but I am seeing a coloration change almost like a dark scarring. Is this the dye breaking down and the natural coloring poking through?

We are using both powdercoating and anodizing on our frames which are stacked and unstacked frequently, thus the tubes are banging off of each other. After two years in the field the anodized tubes look terrible and the powdercoated tubes look almost brand new. This is counterintuitive to me after reading all of these posts.

Even though anodizing is the hardest is it fair to conclude it is not the most durable dependent on the application?

Your experience and insight is greatly appreciated.