Interference fit - bronze ring/sleeve into aluminum

[MBam]

I need to put a bronze sleeve into an aluminum casting to repair a corroded surface. At least I would prefer to use bronze as there is salt water involved. However it might be that bronze won't be suitable due to the difference in thermal coefficient of expansion between the casting and the sleeve over the 100F change in temp that this normally sees.

I'm trying to figure out how much interference to use and how much the ID of my sleeve will change once inserted so I can arrive at something close to my desired size. I also plan to use loctite on the od of the sleeve.

If bronze is not suitable then the same question for an aluminum sleeve.

Quick drawing and photos attached.

All comments appreciated!

 

[JohnRBaker]

If the OD of the bushing is the 7.603 dimension, I suspect that there may be more deformation of the Aluminum housing than in the Bronze bushing itself. Also, with dimensions this large, the difference between the thermal expansion of Aluminum and Bronze, over a delta of 100˚F, could be a real issue.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
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[SwinnyGG]

Regardless of the CTE mismatch, aluminum and bronze in contact with each other and saltwater is not a great plan- you'd be creating a galvanic couple with a potential of around 0.5V depending on specific alloys. That's high- corrosion of your assembly will just accelerate.

That pushes you back toward an aluminum insert, which won't have a CTE mismatch if you use base stock of the same alloy. Machine your insert to be a slip or transition fit with the bore at final size, and retain the insert in the assembly with sleeve retainer.

 

[EdStainless]

The comment about corrosion is on point.
Even if you use a different Al alloy (for higher strength or better corrosion resistance) the differences will be minimal.

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P.E. Metallurgy, Plymouth Tube

 

[MBam]

I gave the corrosion issue a lot of thought. Here is a link to a site that explains the problem well.

http://www.palmbeachmarinediesel.com/heat-exchangers.html

The bronze/aluminum joint does not see salt water. It is normally exposed to ethylene glycol/water (antifreeze).

When the o rings (as described in the link below) start to weep saltwater it is the ID of the sleeve that will see salt. I am thinking the bronze will be better in this scenario.

 

[EdStainless]

If that is truly the case then look at a Al bronze or NiAl bronze.
Are you sure that the Al will not corrode in the EG?

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P.E. Metallurgy, Plymouth Tube

 

[MBam]

I have some 954 aluminum bronze on the way. A lot of the components in the cooling system are bronze, copper or aluminum so I think the EG will be ok.