I wasn't sure how quickly the Zn would react with the HCL either. Our chain has a zinc anode near the anchor, so to check I put that in first and let it soak for 10 minutes. The zinc appeared unharmed (although bright and clean). Keep in mind that the Muratic Acid sold at Home Depot isn't terribly strong.
JWagamon is correct, be careful with the stuff! I used chemical resistant gloves, safety glasses and long sleeved shirt and pants.
If your chain is in good shape (no rust) I wouldn't recommend this treatment.
It was a waste of time since now we've decided to have it regalvanized.