When two different metals are in contact with eachother, and also both in contact with an "electrolyte" (such as salty perspiration), then so-called "galvanic corrosion" can be set up. This may show as pitting of the plating, or an errosion of a patch of base metal (what is beneath the silver plating).

This problem becomes more severe, the further apart each metals` "electrode potential" is in the "galvanic series"

Hope I haven`t lost you. More simply, to avoid corrosion, the metals in the following list should have numbers that are as close as possible"

From http://www.engineersedge.com/galvanic_capatability.htm

Gold 0.0
Silver 0.15
Silver Solder 0.3
Copper/Nickel alloys 0.35
Brass 0.4

Judging from the preamble at the site, the difference should not exceed say 0.15 or 0.2, given the exposure that many instrument have to moisture and other contaminants, including salty material, which greatly compounds the corrosion problem.

With the combination of gold and nickel/copper, that we have a difference of 0.35.

It would seem that the use of gold plating over nickel/copper alloys - i.e. flutes that are not sterling silver or gold - provides a situation where we can expect a marked increase in galvanic corrosion.

I did this little research following a comment in another forum that a technician had noticed more pitting corrosion on gold-plated saxophones.

That reminds me... I was going to post pics of my Armstrong.

I`ve never seen a corroded Gold flute before, but here I`ve uploaded pictures a corroded silver plated flute. The Keywork aged gracefully in 30 years, but that body... ugh. The corrosion areas on the body of my flute happen to be the area one is most likely to miss while cleaning their flute. In time these area may tarnish, pit, and get horribly ugly.

http://www.flickr.com/photos/sylvangale/

Thanks Piko, it`s nice to have pictures to look at. You seem to be having a lot of fun playing!

Corrossion happens from outer influences,body acid, bad climate or poor maintenance.

Plating can corrode and be cleaned and replated. Plating does much more to protect against corrossion than cause it. It keeps out the climate from touching the inner metal.

The plating is kind of like a reminder to get it replated. If someone sees a patch missing, they should get it replated. Acid in peoples bodies eats away at material. If plating wasnt there it might eventually leave a hole.

It is not uncommon to se professional Brass instruments with gold plating,according to your chart that would be the worst for corrosion. Yet there is little evidence professional gold plated instruments have a larger amount of corrosion. Possibly because pros take much better care of thier instrument.

On the saxophones did he mention exactly where the corrossion occured? Or what climate he is in? Was the plating corroding turning green or red? Or just pitting?

The are many variables as why this happens.
I would still rather have the plating get eaten away or corroded than the inner metal.

Actually I did a little websearching and found most things for sale that are gold plated brass are sold as corrosion resistant. Many audio adapters are like this.

I would still be interested in the Tech who mentioned this. Possibly his shop is located in a costal town(salty air is notorious for corrosion), and gold plated instruments are most likely owned by professionals. Professionals sometimes tend to play long hours,nearly every day in smokey bars(maybe while drinking),smoke, alcohol and constnat use are all factors. Maybe all the orchestra players go to another shop and all the nightclub giggers go to his shop.

Still way too many variables but interesting thought.
What forum was this on? I would like to check it out.

gold plating can affect the flute if it is pierced and the matal below is exposed.
This is as a result of sacrifical protection where metals which erode quicker give electrons to the gold to prevent it from corosion.
however this wold not affect the flute unless the gold plating were penetrated in some way.

I do love playing the flute. It`s hard to imaging what life would be like without a little music in it.

Just to get back on topic... found an article on "Red Plague". Didn`t realize the metal on metal corrosion was so common.

http://www.corrosion-doctors.org/MatSelect/corrsilver.htm

And that Gold is always used for a Gold plating effect:
http://www.cybersax.com/BellWashes.html

Should have read "Gold isn`t always used"