Objective: How can you clear rust off a screw or nut head?

Which of the following solutions is more sound in terms of naive physics reasoning?

Pick your answer from:
- Pour Cocoa powder on it, let sit a few min, then clean off, repeat until rust removed from grooves of the head of the screw.;
- Pour Coca Cola on it, let sit a few min, then clean off, repeat until rust removed from grooves of the head of the screw.;
Pour Coca Cola on it, let sit a few min, then clean off, repeat until rust removed from grooves of the head of the screw.