Alien- Own Blood

His hope was that they could create a Xenomorph with chameleon-like properties, and then transition the science to armor, much as they’d previously done with the acid-resistance experimentation.
That breakthrough had been based on the Xenomorphs’ resistance to their own acidic qualities. One of the strongest corrosives in the known universe, the creatures had it inside their bodies both as a defense mechanism and to carry nutrients. How something could eat through metal, and not eat through skin and organs, had flummoxed the scientists until the late Matthews had analyzed the Xenomorph DNA. He had been able to pinpoint the gene that made it possible.
Thus gene-splicing armor was made from the lab-grown skin of a Xenomorph.

Infiltrator, Chapter 29