Originally Posted by A990
Originally Posted by AAR#2
Originally Posted by kentj340
Originally Posted by steve70
Here's a couple pics of an NOS case


Sure looks to me that those parts are coated with yellow Alodine. I'm pretty sure Jim Ridge is applying yellow Alodine during alternator restorations.

About 10 years ago I sent Jim Ridge my double pulley alternator for restoration. Jim advised the case had been sandblasted by a rebuilder, was unsuitable for restoration, and he would need to find another that had not been blasted. He found another good case, and he took the photo below with double pulley in his shop at completion. Note the case finish with double pulley is without Alodine.

Later I realized my alternator should have had a single pulley, so I returned it to him to switch the pulleys. He told me that he had only recently learned Chrysler alternator cases had a finish different than the one he had previously put on my alternator. He said he would put the new finish on my alternator along with the new single pulley. The new finish is shown in the photo taken by me of the exact same alternator with single pulley. Unfortunately the lighting is not the same as Jim's photo, but I strongly believe that he had applied yellow Alodine. Note the hint of rainbow appearance.

Alodine is sold two ways, as a clear solution without dye, and also with a yellow dye added. In my experience, the yellow Alodine eventually dissipates in an engine compartment environment, but is easily renewed in place with a new brushed-on coating.



I can see how you may suspect Alodine 1201 but I’d place a bet on Alodine 1001 for the “added finish” bottom photo. To get the color in that photo it would have been in the bath for greater than a brief dip. Alodine 1001 will darken your aluminum a bit but leave it well protected, 1201 will produce a yellow to golden/brown color that is very apparent. I’ll state that color is the result of strength of bath and time in solution but 1201 would need to be diluted well beyond manufacturers mixing recommendations and dipped only briefly, potentially leaving the surface unprotected, and not a process adopted by a manufacturer.

I vaguely remember years ago that folks were of the belief the aluminum was bare, and believe Jim was of this position as well but changed some time later after rebuilding a low mileage alternator and/or starter and discovering there indications of protection on the surface, If you consider the exposure the aluminum on a starter body would experience during a salty/wet winter (anywhere but the SW), the aluminum body would degrade very rapidly. I realize this thread is about alternator cases but use the starter as an example due to its more severe exposure and like base material.

I used to treat aircraft parts with Alodine. The one I used would range from golden to dark brown, depending on exposure time.
It sounds like some experimenting on spare parts is needed


Yes, aircraft parts are never done with Alodine 1001. The reason aviation uses 1201 is because it provides a clear visible confirmation that the part is protected. Automotive isn’t as worried about the visual

Again, I wouldn’t recommend using 1201 on an automotive part if your goal is “as delivered from the factory”