Do you remember when your science teacher made a battery from a potato and two nails? The current was generated because each nail had a different electrical potential, and so ions traveled from one nail (the anode) to the second nail (the cathode). The potato contained electrolytes, the medium through which the ions traveled. This process of ion exchange is called galvanic corrosion and it will destroy your tent poles, zippers, bicycle lock, knife, and any other piece of metal in your gear.
While sea kayaking, the ocean is like a giant potato, and your gear are the nails. Due to its salt, seawater is a very efficient electrolyte and every piece of gear, even gear that is never submerged in water, will suffer corrosion. Despite dry bags and watertight hatches, nothing stays absolutely dry on a long trip, and the wind carries salt and sea spray into camp.
During my circumnavigation of Florida, Dan’s tent poles became so corroded that they would not separate and after the trip, they could not be salvaged. We also used bicycle locks to secure our kayaks overnight and the locking mechanisms corroded so badly they stopped working. Zippers jammed, knives rusted. Had we known how to clean corrosion in the field, these problems would not have reached the point where our gear was destroyed.
Fortunately, cleaning corrosion in the backcountry is easy and can be done without toxic chemicals like petroleum products.
What you need
To remove corrosion and salt buildup from zippers, eyelets, and other metal areas of clothing, use a toothbrush to rub vinegar into the affected area. Open and close the zipper several times, scrubbing carefully between the teeth in both the open and closed position. If the corrosion is mild, this may be the only treatment you need. If the corrosion is more serious, fill your cook pot with vinegar and soak the zipper overnight.
To remove corrosion from tent poles, knives, or other larger metal surfaces, pour vinegar over the corroded area and scrub the area with a small brass wire brush. Brass is a soft metal and will remove the corrosion without scratching the surface. More importantly, the microscopic pieces of brass that break off will not react with your gear and cause more corrosion. Do not use steel wool since pieces that break off will cause further corrosion. If the corrosion is severe, soak the item overnight in vinegar. You can add baking soda to the vinegar to accelerate the process, but this is not necessary.
The great thing about using vinegar as a cleaning agent is that it is environmentally safe and can be spilled on the ground or in the water in the backcountry without causing environmental damage. Do not bring WD-40!
If you have run out of vinegar but for some reason have a can of cola handy and need to clean corrosion, pour the cola over the metal, then scrub the metal with your toothbrush or wire brush. Cola contains phosphoric acid, which eats away corrosion. You can do this on your car battery at home too. Remember that cola will leave a sticky, smelly residue that will attract critters during the night, so wash the area with fresh water thoroughly.