Originally an OEM 245mm Magnesium Fan https://pbase.com/image/165233971 which Mark Motshagen milled and sized down to 906 spec. https://pbase.com/9146gt/image/165455510.

After much thought, we decided to leave the Magnesium surface untouched, as original and not treat it with any type of epoxy coatings. This is how it looked like https://pbase.com/9146gt/image/165455515 left untreated, contrasting against the Chromate treated 906 housing. The only treatment to the Magnesium that I'm considering will be a repeated coating of the ZEPreserve product https://pbase.com/image/165272600 (I swear by it!). In my experience, ZEP is a superior product than WD-40 or Gibs and penetrates the Magnesium alloy to better preserve it. Here is a sample photo after the first application of the ZEP product https://pbase.com/9146gt/image/165455530. Note the deeper and more even color of the fan after ZEP https://pbase.com/9146gt/image/165455523 when compared to when left untreated https://pbase.com/9146gt/image/165455513.

Using this 'preservation' approach, the original patina of the Magnesium fan is retained. The other positive aspect is that the Mag fan can always be Chromate treated in the future at any time, but cannot be brought back to original as easily. Mark agrees so we're leaving 'good-enough' alone. By the way, I use a large heavy-duty Ziploc baggy https://pbase.com/9146gt/image/165455521 (sold at Lowes or The Home Depot) to apply the ZEP prodcut over a two month period of time. I keep the Mag sealed in the Ziploc bag during the application period, the ZEP fumes are retain and that helps to speed-up this process. I'll post follow-up photos two or three months from now.

PS: The housing shown in these photos is an OEM 906/RSR Magnesium race part which was Chromate treated by Gary Arentz. Note how close the colors are, the Chromate housing vs. the untouched Mag fan finish https://pbase.com/9146gt/image/165455529. This fan will ultimately be completed with its original center-hub restored, the entire assembly balanced and the center hub properly re-attached with the correct rivets.