Some years ago I made this mini santoku in carbon 1010 and stainless 304 with a 5160 core for an order. I didn't like the way it looked (the inner 5160 core had switched too much to one side), but since it was 100% functional, I gave it to my webmaster so he could use it. He's been using it for a long time and the knife is still as the first day he got it.
I've been getting a lot of questions lately on what extra care is needed for this steels combination, so I asked him to let it rust on purpose and then document the cleaning process to show how easy is to maintain one of these kitchen knives.
Knife used to dice potatoes, left intentionally unwiped and with water over it for about 24 hours. (Picture 1)
Close up. You can see rust in different stages. (Picture 2)
First step. Soaking a paper towel in tap water. (Picture 3)
Once you swept the blade with it. (Picture 4)
Resulting blade. This will usually take care of ALL the rust on the blade if you just forgot to properly dry the knife or forgot it on the kitchen top a few hours unatended. (Picture 5)
In this case we need to go an extra step because of the severity of the rust. For this we use regular kitchen steel or brass wool (Knife in the background is already clean because this picture was taken afterwards)
We grab the knife, wrap the wool over the blade and pass it back and forth several times under running water. In this particular case, for a whooping 30 seconds. (Picture 6)
This is the knife right after we finish. (Picture 7)
Now dried up. (Picture 8)