There is a give and take with high carbon steel. Give a little love with each use and maintain a naturally beautiful, highly functional blade in return.
High carbon steel will rust if left wet indefinitely. So, rule one, don’t leave your knife wet from food or washing. Keep a dry to damp towel on hand. When you have finished a cutting task, have just washed or rinsed the blade, give that knife a wipe down!
High Carbon Low Alloy
Never put a knife in the dishwasher. This is destructive to the knife, just don’t do it.
Patina vs. Rust
Keep that blade dry, avoid rust, watch a healthy patina develop. Patina is our friend. As we start to use the knife we get to watch a beautiful transition. Acids in the food will cause a chemical reaction in the steel and I love it! It’s so cool to see all the beautiful reactions on the surface of our blade. Ultimately a fully formed patina is grey to black and will help protect against rust to some extent. If you use your knife regularly you may see the formation of some small spots of red oxide (rust). In this case use a scotch-brite type scrub, continue using and caring for the knife normally.
Protect your knife.
Lastly, protect your knife with a coating. If the knife will be left unused for a while it can pickup moisture from the air which will lead to rust. This is easily avoided by a light coating of oil. Any oil will do in a pinch, preferably a food safe oil. Mineral oil is recommended as it is food safe and will not go rancid like other oils found in the kitchen. Heck you can butter the thing if you have to, but again I recommend stable food safe coating such as mineral oil or Axe Wax.