[C320-list] Pulpit / bowrail rust

[Dave Hupe]

 I highly recommend "Spotless Stainless"  Amazon.com: Spotless Stainless Marine Rust Remover and Protectant - 16 Ounce (Pint) : Automotive  It is pricey, but it goes a long way since it is a gel.  Just put it on with a brush, keep it wet for about 1/2 hour, and then flush off with water. 
I first used it on our home stainless steel oven and it worked great.  Obviously I couldn't spray water to remove it, I just wiped it off with wet cloths.  I have since used it several years in a row to clean my stainless propeller shaft and my propeller (it is fine in bronze). The pint=sized bottle has lasted several years. 
Practical Sailor recommended Spotless Stainless as the best available for this.   They say you also can make your own "home brew" as follows (but I don't have experience trying it):
Gelled Citric Acid Passivating Solution   
   - 10-20 percent citric acid
   - 1-2 percent by weight fumed silica

Dissolve the citric acid in warm water. Add the fumed silica (also called Cabosil M-5) and mix. A simple rule of thumb is 1/2 cup of fluffed fumed silica plus one cup of the citric acid solution. This will make 1 cup of gelled passivating mix.  For a thicker solution add more silica. For a sprayable solution that will cling and not bead up, add less.

Citric acid is available in grocery stores or online. Fumed silica is available through chandleries, fiberglass supply houses, and online. We bought a 15-pound bag 10 years ago, and we’ve been working our way through it ever since, thickening epoxy and cleaners.
Dave Hupe
1994 C320 (#32)