Nickel works great. My vinegar mixture turned light green within the first 10 minutes of feeding. Part. Make sure the part you are covering is clean and polished. Nickel will not fill scratches or adhere to rust/grease. Your part must be flawless, if it becomes dull a quick brush with 0000 steel wool will bring a shine. I left it in the water overnight and it only rusted in places I didn't properly prep.