Est. 1998 — 27 years of woodworking knowledge
pits in cast iron tool tops
Howard Pollack
I purchased a couple of used tools that have rust pits in the tops. I can deal with surface rust easily enough, but how to remove the rust in the pits and keep them from getting rusty again? I live in a very humid place and need to be vigilant regarding rust. Any help will be appreciated. -Howard
Re: pits in cast iron tool tops
kneale brownson
I've used those ScotchBrite scrub pads and thinner to eliminate rust from shallow spots. I've used TopCote to prevent reoccurrence. My stuff sits in unheated spaces in Northern Michigan, so there's plenty of humidity. Wax will preserve too.
Re: pits in cast iron tool tops
Jim DeLaney, Austintown, Ohio
Fortunately, that hasn't happened to my tools, so I have no first hand experience - but what about pitting a few drops of Evaporust on/in the pits to dissolve the rust.
Perhaps a bit of 'Naval Jelly' rust neutralizer would also work.
First +
Mark Mandell - Gone Round In New Jersey
Phosphoric acid. Sold as "Naval Jelly" , "Must For Rust" and several others. This chemically changes Iron Oxide (a/k/a Rust) to Iron Phosphate and dark gray crystalline compound that halts further oxidation in those pits. Now with a flat block wrapped in wet/dry 400 grit paper and mineral spirits, carefully rub down, bu hand the top. Wipe clean, and treat your surface. Boeshield is great if your humid, but I use my friend Johnson's.
Lastly, get a dehumidifier going in your shop; preferably one with a pump included or draining either outside or into a small condensate pump like is attached to a furnace A/C coil, so you don't have to worry about emptying the thing..
Re: First +
paul in AZ
Of the various phosphoric acid treatments the more liquid [watery] type is better than the jelly.
Being very liquid it flows into all of the tiny cracks and crevices in the rusted area. And, excess can be easily wiped up after a period of soaking.
Now some trivia: did you know that they use a phosphoric acid as a rust killing primer on the Golden Gate Bridge? It works.
electrolosis
Jack Guzman from Maine
Get a bit of washing soda and a 12v battery charger. Works every time on hidden rust. I've been using this on old tools for many years. There are a few articles on woodcentral on how to do this. It is a simple setup.