Hi Canopy,
I see you are in Thailand, which is in the Tropics - latitudes of much higher humidity throughout the year than we experience in the Northern or Southern Temperate zones. I lived in Sumatra Indonesia for 2 yrs a few degrees N of the equator. The air humidity hadn't been below 66% in 100 yrs and was more frequently 85 - 100%. There are 2 seasons, the "Dry", when it rains small amounts,in local moving cloudbursts every day. And the "Wet" season, with the arrival of the monsoon rains when it rains lots, hard and steady over wide areas for hours a day, every day.
Steel tools need special care and protection, and frequent use helps. Remove all rust, then immediately coat thoroughly with oil or grease, boiled and strained lard or bird fat can be good. Don't try to hard coat them with wax or acrylic or varnish, wax wears off too easy and is a PIA to apply, and water will get under the other two and start to rust your steel. Whenever you're not using your chisels, wrap/roll each in oilcloth to continue the oil protection barrier from humidity. I like flannel saturated, but not dripping. Then put them in a roll-up pouch of leather or nylon. Keep a pc of cotton cloth for wiping them off as clean & dry as you need each time you're gonna have em in your hands.
Hand and brow sweat is good and oily, but also salty, so wipe the salt off and re-oil or grease when you're done for the day, including the cutting edges. Same treatment after sharpening, esp if you use a water stone.
Traditionally, other metalware for cooking and eating and storing is brass, tin or Bankah tin (pewter) in Sumatra. These alloys resist corrosion from humidity much better than steel or iron. The two most common steel edged tools were the machete and the chunkel (similar to an asadon in Latin America). Daily use and greasing/oiling kept ahead of the rust. That was out in the lowland rainforests before stainless steel came into use. I hope I never see a st st machete. It'll get dull fast and be dangerous.
Where are your chisels made? Where in Thailand are you? Is democracy comin'?
Steve