Correct finish for rear stub axles

[indescikov]

Hello All,

What is the correct finish for the rear stub axles, both the constant velocity side and the drum/wheel side?
This is a 1970 car
What I have found so far suggests "black oxide".

Thanks in advance

[gled49]

It's actually phosphating which creates the flat, black finish.

[Robert5995]

I'm with Gled - black phosphate!

- Rob

[chris_seven]

Just for information there are two main types of 'phosphating' applied to steel and both are available in either black or dark grey finishes.

Zinc Phosphating which is easier to apply and generally lower cost provides a porous surface which assists with corrosion protection as it will hold an oil film quite well.

The better finish is Manganese Phosphating which produces a much harder film than Zinc, it produces good corrosion resitance, anti-galling charcteristics and improves lubricity.

It also continues to provide continued wear protection even after break-in and is better than Zinc Phosphate in this respect. It would be my choice for any parts that have to withstand adhesive wear and involve sliding surfaces.

Phosphating does cause a small dimensional change and many parts that use this finish have a 'process grinding' allowance to maintain 'fit'.

Black oxide will produce a 'shiny' black finish compared to either of the phosphating processes but will produce little in the may of corrosion protection. It does not cause any measurable change of size.

It is fairly abrasion resistant and good for 'indoor' applications but should only be considered as decorative.

I would also consider baking any high strength steels (Hardness of 40 Rockwell 'C' and above) that had been treated with any of these processes to eliminate any potential Hydrogen Embrittlement.