Thread: Anti-scaling compound--two thumbs up!

I've read mixed reviews of different anti-scaling compounds, so I thought I'd order some and see for myself how it works for me. I got the PCB anti-scaling compound from USAKnifemaker.com, which costs about $20 per pound.

Anti-scaling compound is used during heat treatment to prevent the steel from coming in contact with oxygen. At heat-treating temperatures, steel reacts almost instantly with oxygen and forms this nasty, super-hard substance called scale. It's kind of like instant rust, and it causes the metal to bubble on the surface and flake off in big chunks. It's a real bear to grind off when it occurs.

This evening I gave the PCB a try with my new heat treating oven. I heated two blades up to about 800 F, then sprinkled the compound on with a spoon. It was more difficult to do this than I expected, especially with welding gloves on, so I ended up with an uneven coating. In the places where it was thick enough, it melted and bubbled, eventually smoothing out like glass.

This was factory-spheroidized O1, so I just did one normalizing cycle, then a 15-minute soak at 1500 F and a quench into Parks AAA oil. After the blades cooled, there was no warping, even though the edges were ground to about .015". (I went a little thinner than I intended there. I've gone as thin as .010" with no warping, but if the grind isn't even the edge can start to "potato chip," or get waves and ripples. This is a good way to make an 8/8 into a 6/8.)

I cleaned the blades by soaking them in some near-boiling water, and I was very pleased with the performance of the compound. They came out almost cleaner than before the heat treat. If I had gotten a little bit better coverage, one of them would have been practically ready for the buffer.

I need to experiment with better ways to apply the compound. I made a little shaker out of a jar with some holes drilled in the lid. If that doesn't do it, I'm just going to buy an actual salt shaker, as the powder is really fine stuff.

You guys who heat treat in forges could probably really benefit from something like this. My heat treating oven is much gentler than a forge, so you might still get some scaling, but I imagine it would be greatly reduced.

I'm very glad I tried it out.

Josh