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Hard anodising and seal anodising

May 20, 2010

Hi,

I have just received some parts from a manufacturer which are supposed to be:

- hard anodised, clear
- seal anodised

The material is 7075 T6 aluminium.

Some of the parts have come back nice & shiny as previous examples have, however others have come back matte & porous. I suspect that not all the parts have been seal anodised, but my background is electronics so I'm not sure what I should really expect.

I'm particularly concerned because these parts will be used in sea-water at significant depths.

Alan Burchell
buyer - Durham, United Kingdom

First of two simultaneous responses --

I would be more prone to think that they had been stripped and re-anodized or excessively etched in the pre anodize steps.

James Watts
- Navarre, Florida
May 21, 2010

Second of two simultaneous responses --

Chloride in sea water attacks sealed anodizing in time. Chloride in sea water attacks UNsealed anodizing FASTER. Chloride in sea water attacks bare aluminum very very fast. You need to switch to powder coat.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

May 21, 2010

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