Aluminum and Steel being mixed....

[Robert M]

There is probably an easy explanation but here comes a question about steel and aluminum. In another thread about "dressing the Scotchbrite wheel" the question abut fine slivers of steel getting mixed with the aluminum would cause corrosion. If this is true..... The HS and VS hinge brackets are match drilled to the spars. These are powder coated but after the hinge brackets are drilled, any powder coating is gone from inside the holes. Then when they are riveted in place there is an aluminum rivet making contact inside the steel bracket. Why doesn't this become a corrosion prblem? Is it because the contact point is sealed from the evironment?

 

[AlexPeterson]

Dissimilar metal corrosion needs an electrolyte - water, for example. If the joints are kept dry, they will do just fine. Van recommends using a light white grease in the case of the spar bolts for that very purpose.

 

[wfinnell]

Here is my question. Why can we NOT use the file to dress the Scotchbrite wheel that will later be used on the aluminum but we CAN use the steel file directly on the aluminum? For that matter we use a lot of steel tools directly on the aluminum, files, drill bits, sheers, saws, hammers?

Bill Finnell

 

[mlw450802]

Here is my question. Why can we NOT use the file to dress the Scotchbrite wheel that will later be used on the aluminum but we CAN use the steel file directly on the aluminum? For that matter we use a lot of steel tools directly on the aluminum, files, drill bits, sheers, saws, hammers?

Bill Finnell

You could probably use the file to dress the wheel but I believe that would be the last time you could use the file for its intended purpose. The grit in the wheel is much harder than metal in the file.

-mike

 

[Paul Eastham]

Excellent point, Bill...this is why I ignore this folklore about steel on scotchbrite and worry about other dubious airplane folklore instead I was going to name a few examples but decided to not start other flame wars here

Besides, the scotchbrite wheel does such a great job on deburring steel too, it would be a shame not to be able to use it.

Paul

Here is my question. Why can we NOT use the file to dress the Scotchbrite wheel that will later be used on the aluminum but we CAN use the steel file directly on the aluminum? For that matter we use a lot of steel tools directly on the aluminum, files, drill bits, sheers, saws, hammers?

Bill Finnell

 

[Rick S.]

You can use a chisel to dress the scotchbrite wheel, makes a mess and wear eye protection but it make the surface like new.

 

[fodrv7]

Explosive results

I recently read an article about an extremely high temperature flash fire from mixing steel and Aluminium on the same wheel.
Aluminium powder makes great solid rocket fuel.
I shall try and find the article.
Pete.

 

[fodrv7]

6300 degree F fire.

Here is the Australian safety Website with the article.
http://www.hanford.gov/rl/?page=542&parent=506

After grinding the heads of 12 pop rivets the wheel was used to grind iron. The resulting fireball reached 6300F and although it only lasted 1 sec it caused the poor operator 1st and 2nd degree burns.

Pete.