Our company manufactures equipment that requires individual testing prior to painting. When the product leaves our site, the only traceability is in one of the dust caps per unit. The problem is that on occasion we lose a dust cap and traceability and end up re-testing everything twice. Is there a magnetic strip that can contain a serial number and be painted over and then read through a layer of paint? If yes, please provide the information.
First, let me say that I am not an expert on magnetism. However, I do remember that Diet Smith used to say in the Dick Tracy comic strip, "He who controls magnetism can control the universe." It is my understanding that the magnetic material must contact the "head" in the reading device in order to transfer the information. This occurs in tape decks and VCRs and accounts for having to occasionally clean the accumulated oxide from the play and recording heads. If this is true, the answer to your question is no, because the paint would act as an insulator.
Another approach would be using a strip of metallic adhesive-backed tape with the code embossed into it. When I had a real job, we used to apply these tapes to identify painted and powder coated samples in the laboratory for testing. At that time, there were metal tape dispensers that embossed the code as it was fed from the machine. We bought the tape and dispenser from an industrial supply house.