When it comes to grounding - are you doing this for signal - or for protection from lightning?
Best method to ground is to find one point to ground - in my experiences - it's been at the antennas' mounting location - that would be your main ground for the MINUS (Negative) and SHIELD of coax providing such return - at the mounting location. You find and use best bolt to metal procedures as you see fit for your install - but RF power and static spike, pokes and strikes from lightning are best left outside.
If you run power, then static arrestors - like you mention - is not the best way to go, you'll need to use DC SHUNT (wire coil) to remove the static and electrical - near DC pulse onto low frequency RF from the wire (coax) AT the strike location - being the antenna.
Since you're pumping RF thru - the Coil design acts as a choke to RF (high impedance across so it looks like a big resistor to RF) but a DC shunt works to provide a low-resistive path to the lower frequencies and the DC level - so it will seek the easier path being the shunt to ground.
IF you don't use such a method - the impulse itself will cause the arc to form, with no way for this voltage/power to flow across easily - so the spark must form the ionization trail - but the buildup of charge to form the arc then the current release - will kill your equipment and even start a fire from the current pulse.
The arc can also form from excessive RF power reflection or even too much power for the arc to withstand (the sheer voltage presence of the RF wave) can make the spark gap arrestor fire on its own draining and ruining your equipment from the jump, arc and subsequent impedance jump caused by this effect - spark gap transmitter is one design that comes to mind.
If you want to WELD the mount to the location - that is up to you, but the mount itself will need to have its own upkeep - welds do break and it's from the usual sources of torque (Load swaying failing overhead) and striking overhead objects - thinner metals also fatigue and can tear / rip / shred - just plain fail from the weld spot twisting. the base metal on its own.
So, some form of backing and bolting will be needed for the mount. Soldering is really the only options for connection of dissimilar metals - at least its pliable for use in coax.
