Jump to content
Sign in to follow this  

Anodising engine cases

Recommended Posts

hey guys. has anyone here ever done or seen engine cases been anodised before?

im building a mint cr500 engine and was considering anodising the cases,barrel and head.

ive heard that it increases the dimensions slightly but cant see that interfering with the bearing housing diametres.

it also hardens alloy th a degree which shouldnt be a problem or lead to cracking.

what are your thoughts?

colours were to be gold engine with polished silver clutch and ignition cover.

Share this post


Link to post
Share on other sites

The problem is that the cases are cast. Cast aluminum is really hit or miss as to how it looks after anodizing. Depending on the alloy of the cast, more often than not it comes out looking blotchy and a different color than expected. I am an engineer at a metal finishing plant and we see this from customers all the time, they send in cast parts for anodize expecting it to look like a billet part, then are not happy with the results.

As for the dimension change, normal type II anodizing will only yeild 0.0001-0.0002" of growth, which won't affect anything on the cases.

Share this post


Link to post
Share on other sites
The problem is that the cases are cast. Cast aluminum is really hit or miss as to how it looks after anodizing. Depending on the alloy of the cast, more often than not it comes out looking blotchy and a different color than expected. I am an engineer at a metal finishing plant and we see this from customers all the time, they send in cast parts for anodize expecting it to look like a billet part, then are not happy with the results.

As for the dimension change, normal type II anodizing will only yeild 0.0001-0.0002" of growth, which won't affect anything on the cases.

how will the engine heat effect it?

can a alloy case be anodised if it has steel in it?

Share this post


Link to post
Share on other sites

As stated above you would probably be better off painting or polishing cast aluminum. You can make that $hit shine like chrome if you want. Who knows, I’ve never tried to anodize after polish that may work.

Also you may want to make sure your dealing with aluminum. Some bikes like KTM uses Magnesium for their covers.

Share this post


Link to post
Share on other sites
how will the engine heat effect it?

can a alloy case be anodised if it has steel in it?

You can anodize parts that have steel in them, but you have to mask off the steel with paint. Anything steel exposed to the sulfuric acid during anodizing will dissolve.

As stated above you would probably be better off painting or polishing cast aluminum. You can make that $hit shine like chrome if you want. Who knows, I’ve never tried to anodize after polish that may work.

Also you may want to make sure your dealing with aluminum. Some bikes like KTM uses Magnesium for their covers.

Polished cast aluminum is hit or miss. Raw cast alumium always looks rough and dull after anodized. Polished cast aluminum will sometimes come out looking alright if a high quality alloy was used in the casting and if the casting has few flaws. Unfortunately since the casting process is generally used to save money, low grade aluminum is most commonly used, and it does not take dye well after anodizing for a couple reasons.

Share this post


Link to post
Share on other sites
hey guys. has anyone here ever done or seen engine cases been anodised before? im building a mint cr500 engine and was considering anodising the cases,barrel and head. ive heard that it increases the dimensions slightly but cant see that interfering with the bearing housing diametres. it also hardens alloy th a degree which shouldnt be a problem or lead to cracking. what are your thoughts? colours were to be gold engine with polished silver clutch and ignition cover.

Not an easy task for sure....Just getting the parts ready for the anodizing bath is a very specialized process...AL parts to be anodized are cleaned in either a hot alkaline soak cleaner or in a solvent bath and may be etched in a hot sodium hydroxide cleaner (normally with added sodium gluconate) & then dipped in a solution of mixed acids (typcially nitric/sulfuric w/ammonium bifluoride). Steel inserts can get damaged easily due to these processes.

Cast aluminum does not tend to look good due to the impurities in it. For the most part, billet aluminum alloys anodizes best. Copper containing 2000 series are generally the most difficult to anodize (castings) and 5000 or 6000 series are the easiest.

Take the parts you want to get anodized to an anodizing shop & see what they can do for you.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×