You might want to look into dehumidifiers for small gun safes. You can get ones that are designed to be reused by drying them in a low oven. Something like this might serve your needs Barska Safe Moisture Absorber Dehumidifier for Home Closets, Safes, and Cars https://www.amazon.com/dp/B00ZX1OOPI/ref=cm_sw_r_cp_api_i_dGcqFb7TRAEC3
BARSKA Safe Moisture Absorber Dehumidifier for Home Closets, Safes, and Cars , Blue https://www.amazon.com/dp/B00ZX1OOPI/ref=cm_sw_r_cp_api_i_R3RBVVCZ2N4C2XPKEJA4
Chuck some moisture absorbers in if you don’t already have some. Very nice little storage you got. 👍🏻
I live in Florida, very humid, and don't have any issues with my safe or guns. Keep them lightly oiled too. I just use 2 of these
https://smile.amazon.com/dp/B00ZX1OOPI/ref=cm_sw_r_em_apa_glt_fabc_9NFGJ49CSBA8SHWS439F