YO! QC Alan here, who also (somewhat) studied science in high school, here to (hopefully) explain the science behind ooshibu turning into LITERAL MAGNETO!
I think the science behind this mainly revolves around electrolysis and electromagnetism. our stomach acids consist of hydrochloric acid (HCl) which can be ionised into the positive H+ ion and the negative Cl- ion. Due to the iron being molten, it ionises his stomach acids. The molten iron then acts as a conductor to the stomach acid, conducts the negtive ions and becomes magnetised, ig? Which is how ooshibu now has magnetic powers.
Disclaimer: This is just a theory, (A MANGA THEORY!) which can easily be disproven by someone who simply just knows more shit about this than I do. And if you do have a better scientific explanation for this phenomenon, please, reply to this comment, or even make your own comment. I'd love to see your scientific theories!
ANOTHER Disclaimer: Do not drink molten lava. It will not give you magnetic powers. You will simply just die. Ooshibu is just built different. Mainly cuz of his surgeries.
That is all.