I'm writing a novel set in the mid-nineteenth century. One of my characters needs to cause an iron padlock to rust rapidly, ideally within a matter of hours.

The lock doesn't need to rust away completely - the goal is just to make it noisey and annoying so that it can't be opened in silence.

Is this a realistic goal? If so, what methods could someone use to cause rapid rusting? Bonus points for suggesting period-appropriate materials. 

Update: Based on the answer and comments below, it sounds a period appropriate approach would be to mix fine copper filings with saltwater and apply it to the lock.

I've read that bleach is an oxidizing agent which was available in the 19th century. Would adding bleach to this mixture increase the rate of rusting without creating an overly dangerous mixture?

Update: I conducted an experiment in my garage. Iodine worked pretty well.
[Experiment Video](https://youtu.be/t3HrOirO8Ao)

A few months later the iodine had eaten through the lid of the jar I tested it in:

[![Iodine Ate Through My Jar](https://i.stack.imgur.com/dSPS3.jpg)](https://i.stack.imgur.com/dSPS3.jpg)