Zinc Plating Steel to Stop Corrosion with Aluminum

[FINN_imported]

I have a steel shaft which rotates very slowly in an aluminum housing. I have encountered some "galling" and "lockup" between the parts. Will zinc plating of the steel shaft prevent the "galvanic reaction" between the aluminum and steel, thereby reducing or eliminating my "galling" condition?

-FINN

 

[TVP]

Zinc plating the steel will reduce the galvanic couple to the aluminum housing, since zinc is much closer to aluminum in anodic/cathodic potential. However, I am not certain that this is your problem. Galling is a completely separate phenomenon from galvanic corrosion, and I would not expect zinc plating a steel shaft to fundamentally alter the galling behavior of the aluminum housing. Galling would occur because the stresses from the shaft are sufficient to cause local deformation. Why not use a bearing?

 

[etch]

Your shaft might not be properly aligned, if it is a small item of machinery, used used in a workshop or house, why not put a layer of lead between the shaft and housing, this will allow some beddig down of the shaft.

if for more advanced machinery, id agree with TVP and use a bearing

 

[FINN_imported]

This particular piece is for a rack and gear hand actuated hydraulic system. The pinion gear is the part in question for plating. I did not use a bearing as TVP suggested due to non-continuous rotation and for cost consideration. I am still asking the question of plating preventing the "galvanic" reaction between steel and aluminum, or is this process not cost-effective?

-FINN

 

[TVP]

As I mentioned in my first email, zinc plating a steel shaft will reduce the galvanic potential on an aluminum housing. It is defnitely a cost-effective process when large production quantities are concerned, but I don't know how it will compare if you are only having one shaft plated.

 

[MikeMech]

I agree with the others that the galling is most likely a separate problem. However, you can reduce the effects of the galvanic action between the steel and aluminum by applying a liberal coating of anti-seize between the two surfaces. It will act as an electrical insulator and provide lubrication as well. You can get it from McMaster-Carr (

http://www.mcmaster.com/).

I've used it in the past with good results in marine atmospheres on steel/alumininum connections.

A bearing or bushing would be the better solution, though, if you have the budget and desire...

Mike