Gas blocks: like metals?

[wild_wild_wes]

Is there any reason for matching the metals you choose for gas blocks and barrels? For instance, with a carbon steel barrel, should you choose a carbon steel gas block, or will stainless work as well (or better)? I read somewhere where dissimilar metals in close contact can set up some kind of oxidation proccess due to electron migration or something like that.

[GitmoSmoke]

I am far from being an AR-15 expert, but I do have quite a bit of knowledge on dis-similar metal or galvanic corrosion from working on airplanes for the Navy for the past 19 years. In an ideal situation the metals would be exactly the same and sealed from moisture and oxygen. Since this is almost never practical we want the metals to be as similar as possible, with the more corrosion prone metal to be the onr that is easier to maintain, cheaper to replace, or less critical to the opperation of the system. I am sure any of the military aircraft workers recognize this list. It's taken from the military aircraft corrosion manual. The farther apart the materials are the more they will react with each other with the anode corroding away, leaving less damage on the cathode. The higher the moisture level and oxygen level get the faster corrosion will occur.

ANODIC- MORE CORROSION POTENTIAL- High Corrosion Potential
Lithium
Magnesium Alloys
Zinc (plate)
Beryllium
Cadmium (plate)
Uranium (depleted)
Aluminum Alloys
Indium
Tin (plate)
Stainless Steel 430 (active)
Lead
1010 Steel
Cast Iron
Stainless Steel 410 (active)
Copper (plate)
Nickel (plate)
AM 350 (active)
Chromium (plate)
Stainless Steels 350, 310, 301, 304 (active)
Stainless Steels 430, 410 (passive)
Stainless Steel 13-8, 17-7PH (active)
Brass, yellow, Naval
Stainless Steel 316L (active)
Bronze 220
Copper 110
Stainless Steel 347 (active)
Copper-Nickel 715
Stainless Steel 202 (active)
Monel 400
Stainless Steel 201 (active)
Stainless Steels 321, 316 (active)
Stainless Steels 309, 13-8, 17-7 PH (passive)
Stainless Steels 304, 301, 321 (passive)
Stainless Steels 201, 316L (passive)
Stainless Steel 286 (active)
AM355 (active)
Stainless Steel 202 (passive)
Carpenter 20 (passive)
AM355 (passive)
Titanium Alloys
AM350 (passive)
Silver
Palladium
Gold
Rhodium
Platinum
Carbon/Graphite
CATHODIC- LESS CORROSION POTENTIAL

I was thinking this woulden't be relative for firearms, but your question started me thinking about a the 5.45x39 with their corrosive primers. I know many people use hot water to clean out the salt residue. If it wasn't compltetly cleaned and dried we have made a perfect corrosive enviroment. Tight metal contact and electrolyte solution and maybe high temperture to accelerate the process. I will be keeping this in mind if I decide to buy that 5.45 upper I was thinking about.

[wild_wild_wes]

Any other opinions?