Are the GS side covers really aluminum? Why do they corrode?

[sidd]

Ok, my question is this: I'm fairly certain that the side covers on the GS's are aluminum and they are clear coated to protect against corrosion. If they are aluminum which is known to oxidize on contact with air and form a rather strong (though thin, I believe) layer of aluminum oxide, why is it nessisary to protect them further? I KNOW that they corrode, I'm just wondering why. Could it be that the side covers are not pure aluminum? I could see Suzuki using an alloy of some sort to make casting easier.

Any thoughts would be helpful. Thanks.
-sidd

edited to fix typo

 

[morthrane]

I don't know what they're actually made of, but here's food for thought:

Pure aluminum is not used in motorsports that I know of.

Aluminum alloys, on the other hand, are. And the alloy type factors greatly in how resistant (or not) it is to corrosion.

 

[kalessin]

The GS sidecovers that I have experience with (on 1981-1983 G and GL models) have all been plastic.... the ones on my '83 1100GL are cracking and will need some help this winter.

What model/year GS is getting this corrosion?

 

[Guest]

If you are talking about the engine cover then it is probably that they are oxidizing. Sandpaper is made from oxidized aluminum which is very tough.

 

[mixongw]

I think I know what you're getting at here. I lived in coastal Florida for over 10 years. I was a ham radio operator. I had quite a few antennas made of aluminum. After awhile, the anodized protective barrier would succumb to the salty environment and start to form this white powder on the surface of the aluminum. That white powder was aluminum oxide combined with the resulting compound of salt and aluminum. I used to clean the elements of the antennas quite often. It would always come back. Getting tired of cleaning this powder off of the antennas, I decided to let it go. After a few months, the powder formed a uniform white coating and then the corrosion stopped. The coating of powder was protecting the aluminum from further corrosion. However, it wasn't very pretty, at least not as pretty as nice shiny aluminum. I believe this is why all bike manufacturers clear coat their aluminum (alloy) parts; to keep them pretty. I have stripped my aluminum parts of the clear coat and polish them every so often. Mine had some chips in the clear coat that would allow corrosion to start to spread out under the surrounding clear coat. There was no way to get rid of this without removing the clear coat.

Gary

 

[Guest]

Aluminum actually corrodes faster than steel. But while iron oxide is soft and porous, aluminum oxide coatings are very hard and can be non-porous. The soft and porous nature of iron oxide (=rust) allows rust to fall off, and lets more oxygen and salt react with the underlying metal and continue eating it. The hard and nonporous nature of aluminum oxide protects the underlying metal. At the hardware store you can buy sandpaper that uses aluminum oxide as abrasive, so it has to be tough.

Tom

 

[Guest]

This is an interesting subject. It has been my experience, that metals that I had believed to be immune to corrosion still had problems if in particularly bad environments. One of the stranger things was a 300 series stainless steel liner inside of a tray type water preheater for an evaporator. After several years of use it was opened up for inspection and the finding was pretty surprising. You could actually poke a finger right through the liner, as easily as if it was a sheet of paper. This was caused by the chloride salts in the city water combined with a fairly low temperature steam supply for the heating source. I've also seen materials in gas turbine blades, like Metco and Inconel, have corrosion problems when fuel or inlet air was contaminated with very small amounts of elements like vanadium or once again salts. I have even heard of problems with some of the newer superalloys that were designed to replace the old standards. I guess it just goes to show you that some things just aren't supposed to be forever. Keep em clean. Ray

 

[duaneage]

I refinished my covers to original, brushed look and then used clear engine paint over them. Came out perfect.