Got to agree with Andrew here, soldering might not be the best approach. I would go with the crimping a ring tag end to your cable , then securing this with a nut and bolt to the earth stake. Once everything is all nice and tight use a solvent to degrease everything and then seal it up, (allow time for the metal to equalise temp , you don't want to seal any condensation in). I would use a polysulphide rubber sealant, ( because its brilliant at sealing and a twat to get off ).
This is the method we adopt to secure and make all of the Earthing and bonding joints on our aircraft, some of these joints experience extremes of conditions that they would never be subjected to in your average back garden and they last for years and years.
If i was doing this job i'd do it as follows:
1) Cut a new end on the cable, cut off the insulation just enough to fit into the crimp barrel.
2)Clean and protect the bare wire end. I would use De-Oxit D5 to clean and maybe Stabilant 57 to protect.
3) Clean the inside of the crimp barrel with De-oxit
4) Insert wire and make the crimp, following the instructions for the crimp and the crimping machine.
5) Clean and de-oxidise the end of the earth stake and all metal to metal contact points.
6) Make the connection using Bolt, 2x washers and lock nut.
7) clean and degrease the whole area using a solvent cleaner eg IPA, MEK ( my prefrred solvent
) or toluene.
8) allow 10 minutes for the wet solvent and then any resultant condensation, to evaporate.
9) completely seal up the joint. I would use a Polysulphide Rubber sealant ( as i use it all the time at work) but there are plenty of others ( automobile Underseal might do ).
That is pretty much just the way that i would do it at home and the way i
have to do it at work. ( wouldn't bother with de-oxit , etc, at work )
HTH
