20 Stainless Steel Knives

We're doing our best at Rainy Day Forge (Winnipeg, Manitoba.) And the issue that we are facing by using Stainless steel, is heat treatment. We have all of the necessary equipment to do the job, which is an Evenheat kiln to reach those extreme temperatures for heat-treating AEB-L stainless, but now we have to experiment with the barrier to inhibit decarbonisation of the steel. 

When metal reaches high temperatures, in excess of 1400'f, oxygen will begin to leach carbon atoms from the steel. This is bad because, carbon, in combination with iron (and often, other bonding elements such as chrome) is what helps give steel its crystalline structure and hardness. If too much carbon is removed, your steel wont hold an edge and will dull quickly. 

So, how do you avoid this from happening? An oxygen free kiln? Well, essentially yes. But that isn't an option so, what else? 

How to Stop Oxidisation of Stainless Steel

There are a few other options! Stainless steel foil can be purchased in rolls or in pouch form. The knives are placed inside a pocket and stopping oxygen from affecting the steel. Small pieces of paper can be added to the pouchs so that what ever oxygen in the packet is consumed as it burns.

There are also products that can be applied to the steel to inhibit the leaching too. Condursal is one option. It's quick to dry but it stinks like a dozen 12 year old girls putting on nail polish. It's definitely an end of day application and good ventilation is highly recommended. Unless you're a 12 year old girl.

There's also ATP 641 which is a clay that can be coated onto the knives. The downside is that the clay takes longer to dry. If you place it in the kiln when there is still humidity in a clay, the water evaporates quickly and the coating simply falls off the blade. The ATP can also shrink and crack while it dries. This requires multiple applications of clay.  

ATP-641 Experiment

It may take a bit more time to apply but we have a lot of this product to use. We decided to experiment by heating up the blades with a torch and then submerging them into our bucket of ATP. The clay reacted in 2 ways. 

If the knife was at an optimal temperature, the clay would bond to the exterior of the knife and create an nice even coating. Awesome! If the blade was a little on the hot side, the moisture in the clay would steam off quickly and create a pitted layer of clay. When that happened, we spread extra clay on those areas, leaving a smooth coating. 

The experiment is working well. No stink. Quick application. Reduced dry time for the clay. 

6-Months Later

We've stopped the use coatings and are now using stainless pouches to protect our precious blades. From our run of 20 blades, one has shown signs of staining. Not good! We are obviously disappointed with this result.

Here are the reasons why we are now using stainless steel pouches:

• Efficiency Time to make a pouch vs Time to apply a coating
• No dry time
• No mess
• No stink
• Perfect barrier