If you are using washing soda to de-rust (electrolysis) it can be difficult to find Arm & Hammer washing soda in the grocery store. I went over to the Family Dollar store one day, went to the cleaning products isle and found their SUN brand of dry washing bleach and found out it is exactly the compound as the Arm& Hammer brand. I bought some and tried it
on a de-rusting project....worked perfect and also a lot cheaper too!
I found about electrolysis at OWWM site, all the info. you need is there,
tried it and it works really well for getting off the rust with little or no hard work! eezlock