Anodizing Type to specify:

[Briarpatch]

I have to anodize some short pieces of aluminum angle and flat bar that will tie into my mainsheet traveler system.
Should I specify Type II (standard) or Type III (hard coat) anodizing? I plan to specify a class 1 clear finish.

[GordMay]

Depends upon how much you're willing to spend.

Both Type II and Type III "hard" anodizing are very hard coatings.

Type III "hard" anodizing is done at a lower temperature, is more expensive, and a little harder than Type II, but you need special equipment to tell the difference, in practical terms.

Type III, however, is much thicker than Type II, typically .002" vs. .0006" respectively, which makes it more resistant to scratching and heavy wear.

[team karst]

Before that, is the alloy correct for marine use?

[Briarpatch]

It is 6061.

What type of coating to toe rails, masts/booms and other aluminum items are normally specified, Type II or III?

[team karst]

Originally Posted by Briarpatch

It is 6061.

What type of coating to toe rails, masts/booms and other aluminum items are normally specified, Type II or III?

6061 has strength, at the expense of corrosion protection. It contains copper..

[LouK]

Type 1 anodization typ for exterior use, Type 2 for interior use, at least for buildings that is.

[jmschmidt]

Anodized aluminum conducts electricity as well as un-anodized aluminum. In a salt air environment, on land or sea, this allows the salt particles that collect on the anodization to covert to miniature batteries and eat holes in the anodizing and the rest of the aluminum below it. Modern power-coating is tough, durable and is not a conductor of electricity. It provides electrical insolation to protect the metal underneath from pitting and disintegrating.

[dfelsent]

Hard coat anodizing is an electrical insulator not a conductor.
It is subject to micro cracks and pores which is why the coating process should involve a sealing step. This helps fill in these pores and microcracks.
Poorly controlled machining or finishing prior to anodizing will result in poor corrosion resistance.
Improper insulation or treatment of post anodizing machining will also result in corrosion.
A good quality anodized surface can last decades in a New England ocean boating environment.

[David B]

Originally Posted by jmschmidt

Anodized aluminum conducts electricity as well as un-anodized aluminum. In a salt air environment, on land or sea, this allows the salt particles that collect on the anodization to covert to miniature batteries and eat holes in the anodizing and the rest of the aluminum below it. Modern power-coating is tough, durable and is not a conductor of electricity. It provides electrical insolation to protect the metal underneath from pitting and disintegrating.

Actually anodising is an electrical insulator. Where good thermal conduction is required, and anodised aluminium insulator is often used between semiconductors and the heatsink (which is also usually anodised, but not so well).

[GordMay]

Originally Posted by David B

Actually anodising is an electrical insulator...

Indeed.
Aluminum Anodizing is an electrochemical process that creates a thin aluminum oxide [Al2O3] film on the surface of aluminum substrates. The resulting anodized film is electrically non-conductive.
See ➥ https://cdn.ymaws.com/anodizing.site..._2-03_Effe.pdf