stainless and brass

Brass is mostly copper and zinc. Bronze is mostly copper and tin. There is an aluminum bronze. There is still a mismatch, but not as extreme a one as aluminum would give.

Go to someplace like MSC or McMaster-Carr for screws in the proper thread and head and of the alloy of your choice.

Enjoy, DoN.

Used on boats in salt water stainless screws in an aluminum spar (for example) and not insulated will cause the aluminum to corrode. The usual solution is to use any of the available "insulation" sealants when installing the screws.

Brass is a mixture of copper and zinc and doesn't react so quickly with SS.

To get a better idea of what materials to use look at the galvanic tables. The further apart two materials are in the tables the more corrosion will occur.

Note that the corrosion is electrolyses and doesn't occur unless there is an electrolyte (salt water) present.

Cheers,

Bruce (bruceinbangkokatgmaildotcom)

I don't see a big problem with Stainless screws in Brass nuts if the plastic of the gas tank is blocking any galvanic corrosion current flow - the Pem Nut is an electrical "dead end". But you should be able to find 1/4"-20 screws in Brass to be sure.

Either way (Brass or Stainless screws) put some silicone seal or low-strength threadlocker on the bolts to seal out water that could cause corrosion. Because if the threads get stuck, too much force to remove the screws will spin the molded insert in the tank plastic and effectively destroy it.

Brass is primarily Copper and Zinc. If there is Aluminum in Brass, it's only small amounts, and only in special corrosion resistant and higher strength alloys.

Bronze is primarily Copper and Tin.

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DoN, Bruce, & Bruce.

Thanks for the responses. I somehow thought brass was made of the wrong stuff. So I got that straightened out. The original bolts were plated steel. I found a galvanic chart and it looked like SS was a better choice than that. There will be water involved with washing, but never salt water. I lathed up 2 new spacers since the others were too small (I.D.). Then using blue loctite put it all together.

Now the triple clamp hits the tank when swinging the handlebars to one side. I either have to mill off some of the clamp, or heat up the tank enough to smoosh it in a bit. A friend says that the tank is one step above wax. He's heated it up before and added clearance for his exhaust. I got to check with him on how to do that again.

Wayne D.