Fuel Tank mounting screws

[PCHunt]

Getting ready to put my fuel tank back on my RV-6 after leak repair.

The question is: Could I use stainless steel screws instead of structural steel screws. Or perhaps structural stainless screws?

Thanks,

[Vac]

Assuming no tensile strength issues, galvanic corrosion using stainless and aluminum is your biggest concern. There are some dielectric compounds that can be applied to help mitigate this.

Here is a previous discussion on the topic that might shed more light, replies 9 and 11: http://http://www.vansairforce.com/c...t=35651&page=2

Cheers,

Vac

[Deweyclawson]

I always thought SS was less prone to corrosion than steel, galvanic or otherwise.

SS screws are not allowed in structural applications on a cert. airframe as they are weaker than steel. Not having access to the structural analysis for this application, I would use the steel and spot paint the heads if necessary.

[Vac]

Dewey,

You are correct. Tensile strength can be accounted for by hardware selection. The problem is that the aluminum aircraft structure becomes the anode and corrodes in the presence of stainless if an electrolyte is present if the two metals are not electrically isolated.

Even more of a concern in coastal areas.

An easy way to spray paint screw heads: Clean the screws first in a jar with appropriate solution (acetone, MEK, thinner, etc.), allow to dry, drill holes in a piece of cardboard, insert the screws and paint. Chances are you can get quite close to original paint color with appropriate inexpensive rattle can and won't notice the color difference if it's close. Better if you have some original color lying around. Install the screws by hand after they have dried and you won't muck up the new paint.

Good luck,

Vac

[Captain Avgas]

Originally Posted by PCHunt

Getting ready to put my fuel tank back on my RV-6 after leak repair.

The question is: Could I use stainless steel screws instead of structural steel screws. Or perhaps structural stainless screws?

Thanks,

I don't believe that galvanic corrosion is the prime issue here. It's a structural issue.

The cad plated steel AN screws specified by Vans for the fuel tanks are 120,000 psi ultimate tensile. Stainless AN screws are typically 80,000 psi ultimate tensile. So if you use stainless screws in this structural application you are really eating into your safety factor. I'd definitely ask Vans before I opted for stainless screws for the tanks. I think you'll probably find that they will advise you against it.

[PCHunt]

Vans strongly recommended to NOT use SS screws. Tank now installed using structural screws.

Thanks to all!