Home /
Search 🔍
the Site
pub Where the world gathers for
plating, anodizing, & finishing Q&As since 1989


How hard is hard?



I am trying to find out is there a table which will show the hardness of anodised finish's. e.g., Hard @ whatever thickness being equal to a specific hardness e.g., 70 rockwell C. and the same for soft or natural anodised..? We have never been asked to show a hardness before but this customer need's to know. I don't mean to be vague but can someone please help.

Many thanks,

Jim McGeady
- Portsmouth, UK


Good question - everything is relative. As I understand it, hard anodising refers more to the process than the finished hardness. The anodised surface will have a hardness dependent on the type of alloy being anodised. Generally high strength alloys such as 2000 and 7000 alloys can give micro-hardnesses ranging from 250Hv to 350, but 6000 alloys can give 400-500 (or 45-48Rc). However, care should be taken as the hardness of good aluminium oxide can be between 940 and 1100Hv 965-790Rc), but the determined hardness may be only a reflection of the crushability of the alloy substrate. I believe microhardnesses of up to 1400Hv have been claimed from mixed electrolytes, but I have no experience of such systems. As a rule of thumb, hard anodising is considered to be achieved when the hardness exceeds about 350Hv. I think the British Standards specify hardnesses and resistance to abrasions for anodised coatings, but offhand do not know their exact numbers.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully 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 might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact    -    Privacy Policy    -    ©1995-2023 finishing.com, Pine Beach, New Jersey, USA