Aluminum welding wire (AlMg3) for radials on galvanized metal roof?
 

I am about to mount a vertical on a galvanized sheet metal roof. There
are indications that this roof, while farily new and in good shape, may
not be a sufficiently good enough ground plane by itself. So, I will
additionally lay radial wires on the roof. For this I select aluminum,
as I expect (a) low corrosion when touching the zinc-galvanized iron,
and (b) good conductivity of the aluminum.

Readily available aluminum wire would be the kind used for welding,
sold as AlMg3 (aluminum with 3% manganese). Does anyone have
expericence or comments on using this type of wire? Such as:

- The expected RF conductivity? (brief research indicates not much
less than pure Al)
- Corrosion resistance of this material (by itself)?
- Corrosion resistance in contact with galvanized iron?

Other comments?

73 - Kristinn, TF3KX

Aluminum welding wire (AlMg3) for radials on galvanized metalroof?
 

TF3KX wrote:
I am about to mount a vertical on a galvanized sheet metal roof. There
are indications that this roof, while farily new and in good shape, may
not be a sufficiently good enough ground plane by itself. So, I will
additionally lay radial wires on the roof. For this I select aluminum,
as I expect (a) low corrosion when touching the zinc-galvanized iron,
and (b) good conductivity of the aluminum.

Readily available aluminum wire would be the kind used for welding,
sold as AlMg3 (aluminum with 3% manganese). Does anyone have
expericence or comments on using this type of wire? Such as:

- The expected RF conductivity? (brief research indicates not much
less than pure Al)

The surface area of the wire is great enough that you won't be able to
tell the difference between it and a perfect conductor. But it will
still have more resistance than the roof.

- Corrosion resistance of this material (by itself)?
- Corrosion resistance in contact with galvanized iron?

I avoid letting aluminum contact galvanized steel because it quickly
plates the zinc off and allows the steel to corrode. But I'll defer to
people with more experience.

Other comments?

This doesn't make much sense to me. What are the "indications" that the
roof isn't a good ground plane? What size is it, and at what frequencies
are you attempting to use it?

Roy Lewallen, W7EL