You cannot Salt balance to iron the way you Salt balance to the soil, not even if it’s a little rusty Sqaure nail. This is because iron is a solid metallic object. However, you can desensitize it some, to work in your favor!
Say your on 18Khz and ground balanced. Set to disc -30, sweep around and find some iron in the site like buried nails. Small iron grunts. When you find the nails which should be easy if its a house site, a heavy concentration of them is alway's there.
Turn Salt balance on and raise coil up above the nails about a foot, bob coil say from foot to 11 inches above the nails or whatever it takes to barely hear them on the down stroke you want to find where they just start to come in weak. Just a slight wah sound. When it starts to wah pull back up.
You want to find that spot above the nails where they are weak .Right where they begin to be seen on down stroke. Start adjusting your salinity balance up a number and push down maybe just an inch but still having to keep maybe a foot above the nails. Go up a number then check with slight push.
You’ll eventually find a spot where the nails start to get weaker response. Find the spot on the dial that they are the weakest or even does not report at all on say the slight push towards them.This is the spot you want it at then stop adjusting.You can move back out of the nails and do one more ground grab.then your ready to hunt.
You'll still hear the nails as grunts, however they are not gone but they are DESENSITIZED, somewhat to the machine.Think 16 penny nails may look like a 12 penny nail to the machine analogy.Or now, a square nails looks like a finishing nail to it. Maybe not that great but to just give a picture to the minds eye !
Here's what works for me in iron on 18khz for square nails....may or may not work for you in the soil without some tweaking..18Khz, Sensitivity 7,Theshold -2, Black sand off, Salinity about 43, Ground is usually around 800 area.
Sweep speed dependent for best results.think CZ speed.
Use -30 disc to help on troublesome flip flop or ping pong iron.The machine is very good at ID'ing iron accurately.The tiny small pieces of cut nails may call you out but the -30 disc will let you know its flopping. Bigger iron nails on up are actually quieter than a VLF on falsing.
The sonar hit will also tell you its a good target VS a quick sharp ping/chirp of nail false.
Sonar hit has that good round feedback sound.
What's crazy is you'll get a get sonar hit with no iron buzz but open up the hole and investigate and you'll see alot of nails in hole too with the keeper target.
Where as say on your F75 a good hit may be also grunt hit grunt on same target. The Tarsacci isolates the good target and reports only that.Very very quick machine. If it gets a sense of a non ferrous piece it locks on it.
Also targets that are somewhat affected by the salinity balance,,,that is, very low conductors. They will seem to ID more by purity than by conductance.
Foil for example, to the machine will be different than a good alloy like gold or lead or brass etc. Now say foil, on a vlf reads 2 and a pistol ball reads well on Tarsacci the foil can be fluttery or wavy or disappear And foil reading 2 as the salt balance is neutralizing it but the Pistol ball that reads 2 will slap hard.
This is what happens to light iron some of makeup of it is desensitized and the small targets or low conductors jump out better than it can on a VLF where its reading a nail as strong .nail can overtake the pistol ball on VLF but on Tarsacci the nail looks slightly less to the circuit.....SLIGHTLY but in terms of unlocking that's a BIG step.