Best Metal to use against an Anodized Aluminum Body

[majohnson]

Here is what I have; it a hard anodized aluminum body that I need to make a steel or stainless steel plate to bolt up against hard anodize aluminum. I would like something that not going to cause a bunch of corrosion.

 

[memphisjed]

Bronze? Babbitt poured in a pocket gnawed out of a36?

 

[henrya]

Your description is confusing. You say the part bolts to the aluminum body, then that it wears against the body. A picture would help a lot.

 

[majohnson]

The plate bolts to the body then extends forward to hold an internal plate in place that slides horizontally.

What metal works with hard anodizing? It had some type of metal previously, but it worn to bad to reuse.

Thanks!

 

[henrya]

Can you add a very thin piece of plastic between the parts? That would take care of wear.

 

[robert123]

Anodize is an insulator (aluminum oxide is basically sand), so it really shouldn't matter unless it wears through.

 

[majohnson]

Can you add a very thin piece of plastic between the parts? That would take care of wear.

No unfortunately, I can not there is no way secure it. The slot is only .182” in width, so not much room. There is a lot of horizontal movement and if it were to come out it would be a real issue.

Robert,
That what I am trying avoid is wearing through the anodizing and then starting to wear into the aluminum.

Thanks for the replies,

 

[Mtndew]

I would just use stainless steel.

 

[ryancoleman1987]

You have a metal piece that is moving in a channel of some sort in the anodized aluminum?

 

[henrya]

You have a metal piece that is moving in a channel of some sort in the anodized aluminum?

No, we get to keep guessing how to fix his part without knowing what it is. Use your superpowe…

 

[ryancoleman1987]

It has been my experience that hard anodized aluminum stands up quite well to corrosion, but not so well to abrasion. I used to work for an OEM where we made mud pumps. The pump bodies were anodized after machining. Mud under pressure is basically liquid sandpaper, but the the aluminum bodies held up quite well. Unless you let something happen, like the steel liner for the piston work loose. Then the mud would cut through the aluminum in no time.

 

[majohnson]

You have a metal piece that is moving in a channel of some sort in the anodized aluminum?

Ryan,
Correct the plate moves in a .182” slot and the plate it goes into is 3.875 inch long. It hard anodize aluminum, not sure on the which series of aluminum it made of.

I’m just trying to figure out what material I can use that will not create a wear issue with the hard anodizing. Right now I have a plate of 304 SS machined that I am surface grinding a step in. Add 30 degree angles on the corners so if it comes loose it can’t dig into the anodizing and call it good.
Thanks all,

 

[ryancoleman1987]

That's a tough one. I would go with the prior recommendation of babbitt bearing material. I don't know how durable the piece needs to be. It it needs to be stronger, you could always make it smaller than needed, braze brass onto the surfaces, and then machine it to size.

 

[rons]

I use thin teflon gasket. The thinnest I have is .022.

 

[Labrat]

As long as you don't break through the anodize layer, and your environment is not particularly corrosive (salt water or worse), you should be fine with any stainless steel.

What I would be worried about is abrasion. If your steel is soft, the anodize that wears off gets embedded in the steel and it becomes a lap, accelerating the wear. One grain of grit gets in there and it starts the process. Better to use hardened steel but not as hard as the anodize. I would try 17-4PH H900. Keep the interface very clean.

But no matter what you do, any interface with anodize will wear much faster than typical bearing materials.

 

[majohnson]

Thank for the input!!

 

[Bill D]

Are you saying that, in theory, there is no relative motion between the Al and the mounting plate? Or is this plate sliding over the Al for every stroke?
Bill D

 

[majohnson]

The metal plate is stationary while the AI moves to the left and right.