Dissimilar Metal Question

[alldodge]

Had to replace the fuel tank on my dump truck and went to Aluminum instead of steel. Tank comes in and looks good, but has brass fittings in the top. Dissimilar metals tells me that brass and aluminum is not a great thing. Its not terriable but not real good. The brass fittings are for plugs and fittings for the fuel lines.

So do I use some kind of coating on the brass fittings or just change all the fittings to aluminum, galvanize or zinc?

The worst part of the issue is the manufacture of the tank did not know the answer. I was on hold for a while until they found someone who had a slight clue.

 

[Scott Danforth]

if you can keep the salt off the fitting with a good coating of epoxy paint (before you connect the hose) you will be fine.

or change to aluminum fittings.

 

[alldodge]

No salt this is on my dump truck, or maybe your talking about road salt?. You think I need to paint it?

!997 International single axle

 

[Scott Danforth]

Was talking road salt

I would paint the fittings

 

[Grub54891]

You can install stainless fittings directly to aluminum without issue. You can use a stainless bushing between the aluminum and brass also. Per ABYC standards for boats. I see galvanized is acceptable also.


24.18.1.4 TIle copper-base alloys normally used for fuel fittings and lines are considered acceptable for direct coupling with all filel tank materials listed in Table IV, except aluminum Copper-base alloy components shall be separated from contact with aluminum tanks or fitting plates by means of a galvanic barrier such as 300 series stainless steel or galvanized steel. Fastenings used to couple fittings such as fuel senders to aluminum tanks shall be of 300 series stainless steel or equivalent in corrosion resistance.

 

[alldodge]

I would think that painting the fittings might still make contact when torqued but I'm not an engineer or expert on these issues.

My chart shows that SS is better but not as good as Gal or AL

 

[Grub54891]

I would think that painting the fittings might still make contact when torqued but I'm not an engineer or expert on these issues.

My chart shows that SS is better but not as good as Gal or AL

Agreed, all I am going from is the standard, just renewed my certs this year. What chart you have? I'm open to learn something new.

 

[alldodge]

This one

 

[MTboatguy]

I would not even worry about it, both aluminum and brass are inert even in contact with each other, so it would not ever cross my mind to put it back together.

 

[Scott Danforth]

Aluminum and Stainless together should be called eveready.... Add salt and you can watch the aluminium pit in front of you

 

[alldodge]

OK MT, Scott, Grub so I don't need to worry about brass and aluminum, but do I need to paint the tank? If I don't need to then OK, but if I do I will

 

[Grub54891]

This one

Thanks. Alldodge.
About painting the tank, I don't think it needs it, but doing it wouldn't hurt it any. How about coating it with a bed liner type of material?

 

[alldodge]

Thanks. Alldodge.
About painting the tank, I don't think it needs it, but doing it wouldn't hurt it any. How about coating it with a bed liner type of material?

That's an option, and painting it will keep it from standing out, nice shinny tank on old rusting dump truck

 

[Tim Frank]

There is some excellent info. at => https://corrosion-doctors.org/Definitions/galvanic-series.htm

The Coles Notes version is that the environment around the tank will probably have a greater impact than the choice of fitting. The less moisture and/or salt the better.
SS and Al are not a good choice. Brass and Al is much better though still not ideal.

If you are concerned, maybe an intermediate bushing could work well....there are various plastic options.

 

[alldodge]

good link thanks

 

[Scott Danforth]

I was suggesting just painting the fittings and maybe the fitting bung on the tank - basically sealing the fitting to tank joint and the fitting itself. no reason to paint the hole tank unless you want to.

 

[alldodge]

Tank install day, and coating threads with sealer. big chunks of rust comming off