6061 Aluminum Pitting

[crunchie12268]

Hello. I have an application where an aluminum 6061 core is slid onto a 17-4PH shaft, the shaft and core rotate together as the shaft locks the core into place. I am seeing a "pitting" right where the end of the core mates against the 17-4PH chamfer... what causes this? There is a hysteresis brake maintaining tension but that is the only component on the shaft other than some bearings and a housing?

Thanks.

 

[Compositepro]

Probably caused by galvanic corrosion.

 

[CoryPad]

Can you comment on the environment? Galvanic corrosion is a possibility.

 

[sreid]

What color is the pitting?

 

[kumkumvijay]

Hi
Yes, Its galvanic corrosion. Small area of Al connecting with large area of stainless steel will prone for high corrosion than vise versa.

Electrical insulation by insulating material or applying primer or Ti instead of Al can help. If they are rotating part then i hope an insulation is not possible and painting or primer will not withstand for long life. So change of material may be a way to stop the battle between SS & Al.