I still think Oxalic Acid is a safer and better way to go and I would not recommend trying to make it from HCl unless you have a fume hood to work in.
LMAO

I have been trained in safe use of HCL... this is BAD stuff. I use it in my swimming pool to lower pH, ONLY.
I would dump the old HCl on an ant bed.
Oh no I forgot...
Pour on Coke and even beer. Lay the chain in the grass and let the Ants eat the sugar and "jerk their chain" to make the ants mad and they will bite the chain and leave FORMIC ACID.
Then when you are full of Coke and Beer and nobody looking... relieve yourself on the ants, Uric Acid.
Now you run to get toilet bowl cleaner, Oxalic Acid and Tile Cleaner, Carbolic Acid to try to remove the smell and use them.
Then the Admiral gets mad at your drunk, sugar high antics and embarrassing the family and she buys you a stainless steel chain. with YOUR, credit card. Then she doesn't buy Alloy 20 grade stainless chain and you get stress corrosion cracking. She screams at the family wondering where her gallon of Vinegar, Acetic Acid went.
Finally your red neck buddies in your poker club ask you "Hic, wars dat chain to drag widt mah ATV thru da san, hic?"
In frustation, you kick your burnt out, new battery charger to the trash and rub your singed eyebrows from lighting your celebration cigar and getting a hydrogen flash explosion.
Oh well...

Jim...
PS: By a heavy duty polymer rode and don't anchor in coral.