When Breezie mailed me the Sambo pistol to do the Electrolysis on it, I could tell from its relatively light weight that it was made of comparatively thin cast-iron. I know from experience that using high-amperage electricity on such items can cause loss of detail if an iron relic has much corrosion. So I adjusted my battery charger's current-flow to 1/2-amp. Lower amperage means a "gentler" cleaning.
That being said, it was fortunate that Breezie found her cast-iron cap pistol in soil that was "kind" to iron. (Some soil-types are much more corrosive to iron.) What Electrolysis does is break the electrochemical bond which holds the rust-concretion onto the iron's surface. Electrolysis cannot miraculously "put back" iron molecules which have been corroded away. In other words, it is not a magical cure for the rust-pits which often occur while the iron is in the ground for decades or centuries. I must mention that, because I don't want folks to think Electrolysis can make every iron relic you find look as good as Breezie's cap-pistol turned out.
Actually, the most important reason to do Electrolysis on excavated iron is that it not only makes the rust-concretion easy to remove, it electrochemically neutralizes the rusting which has been happening deep down inside the "micropores" in the iron. Electrolysis prevents the iron from continuing to deteriorate after you dig it up. Unlike other metals such as brass, lead, copper, etc, dug-up iron must be cleaned with Electrolysis, to prevent the corrosion from continuing. (Using a hammer to remove the rust-concretion on the iron's surface doesn't stop corrosion from continuing to happen down inside the iron's pores.)
After doing Electrolysis, and any "fine-detail finishing" work that is needed to remove small bits of remaining rust-crust, the iron should be coated with an oxygen-proof sealant, such as Polyurethane. I suggest MinWax "Satin Finish" Polyurethane (not the high-gloss formula). It costs about $6.50 for a spray-can of it at WalMart. MinWax "Satin Finish" Polyurethane is what I used on Breezie's cap-pistol.
