I am in the process of cleaning up/painting a used license plate/fuel door that I purchased online.  Yestereday I disassembled it and soaked the springs, mounting plates and nuts in Evapo-Rust.  I will soak the hardware a couple more days to take care of the rust.
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| About 12 hours of soaking in Evapo-Rust...looks good. | 
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| Also about 12 hours of soaking... | 
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| Well these are plastic but have signs of rust from the springs...working on removing that rust and grime |