Humidity and temperature swings is what causes cast iron and steel to rust. If keeping them in your garage is you only option, make a chest; Chris Schwarz has several designs that are excellent, the dutch tool chest in particular. I have a friend who is in your same situation; he made a wall hanging cabinet with doors that closed well, and put in one of these: https://www.amazon.com/GoldenRod-Dehumidifier-Installation-Operation-Prevention/dp/B07W8JFN2F and it has worked out very well for him. Also, oil your tools with camellia oil, a little swipe with a spritzed rag goes a long way, I use this on my tools which are kept in a closed wall cabinet: https://www.amazon.com/KUROBARA-Tsubaki-Japanese-Maintenance-Camellia/dp/B001TPFVHC/ref=sr_1_2?crid=QMUZ3PBMES7H&keywords=KUROBARA+100%25+Pure+Tsubaki+Japanese&qid=1658494473&s=home-garden&sprefix=kurobara+100%25+pure+tsubaki+japan... and one bottle lasts a long time. Good luck.
You can defenitely find better deals out there, but this is what da_bear is talking about if anyone is looking.
https://www.amazon.com/GoldenRod-Dehumidifier-Installation-Operation-Prevention/dp/B07W8JFN2F
Check out the Goldenrod.
Oil more and this devise really helps. https://www.amazon.com/GoldenRod-Dehumidifier-Installation-Operation-Prevention/dp/B07W8JFN2F
Golden rod dehumidifier