How much experience does
@Josecuervohr have?
This could have a large impact on the method selected. Not knowing the answer to this leads me to think 4metals has made the right diagnosis and answer to the OP's question. As well, yggdrasil has given a simple solution. Throwing out more advanced methods without knowing how well one (such as the OP) knows the chemistry behind this can more often create more issues than it fixes. With 75 pounds of mixed pins, I would use a sulfuric cell, but this may not be much help to newer members just starting out.
@orvi has quite a bit of back ground in using AR in non standard ways, maybe he could add some to the information with the AR/pins questions.