Bob is right, in a fashion. A large number of sources advise use of washing soda over caustic, for amateur usage (like me!), as it is not such an aggressive proces, nor does it pose the same environmental risks of exposure or disposal. Washing soda can be easily disposed of and is not harmful to environment. On a small scale, or where speed is preferred, caustic soda will rip the crud off faster (so say sources that have used both methods), but disposal and exposure do present a problem in large volume. The disposal is an issue for me. I don't have anywhere to pour hundreds of litres of contaminated material, whereas washing soda does little harm if dispersed onto bare ground. In my case, I would need to run a pipe or hose of roughly 40m length, so that disposal occurs behind my farm dam, not straight into it!
All those concerns aside, my experience with caustic soda and a 2.5 to 3 amp charge, has produced dramatic results in a short period of time. I don't expect washing soda is as timely under the same circumstances. With the volume of tank, and manner of process I will be using, speed (or possibly better described as aggression) is of no great concern, provided I can start one weekend and remove, finished, the next. So the washing soda does have some advantages, and caustic soda has others, while acknowledging the negatives.
With regards to Washing Soda for electrolysis, instead of caustic soda, the following sites give straight forward information on setup of equipment and theory involed. There are slight contradictions between the two sources, but I suspect these are due to respective results of the authors.
http://www.robotroom.com/Rust-Removal.html There are a number of pages to the article.
http://antique-engines.com/electrol.asp This one is quite short and to the point. It also speaks about making washing soda from baking soda.
After a wider search, I found great discrepancies in the amperage suggested. Some say 2 amps sufficient, some 5 to 6, some much higher, and one even talks about using the power source of an arc welder! Ouch. The power bill would be huge.
Having never bouht washing soda, I looked into availability. From what has been written by others searching, there seems to be a theme. The larger grocery stores like Woolworths & Coles have apparently cut this line, while the small independent stores like IGA may still carry it. Also, the soda in powder form s recommended over soda crystals. It's said to be quicker to disolve.
If all this caustic VS washing soda, low VS high amps, 'do this' VS 'do that' gets a little tiresome.......me too. I guess the only way to see which one is best results, and lets face it, that's what is important to me, is to do trials on both chemical types and at various amperage. It'll be quite fun to do such experiments. Takes me back to my school days, in science class. Hopefully this time nothing catches fire!
I'm keen to give the alternative a trial. At least I know it won't eat my lungs away!
Does anyone know what the engine cleaning guys use?
If washing soda shows to be anywhere near as good as caustic, it'll work for me, because I plan to run the process over such a long period of time. I only hope that oxidising overnight doesn't counteract the de-rusting benefits during the day (solar panel, remember).
I'll see if I can find some washing soda next week. Lets see how it goes.
Good on ya, Bob!
Lastly, have a look at this impressive setup, by one industrious fellow.
I like this very much. Good way to ensure 'line of sight' reaction!
Added 2040hrs: This is a very comprehensive article to read. Highly recommended
http://myweb.tiscali.co.uk/andyspatch/rust.htm