Soften scale with vinegar?

N

Nicolas Joseph

Joined
Jun 2, 2018
Messages
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Hi, i just heat treated my first knife that I made out of 5160. The oil quench has left an extremely strong scale on it that i'm having a hard time sanding out. I've heard that you can put the knife in white vinegar to soften the scale. Is this true? My worries are that the vinegar might damage the steel in some way or possibly soften the steel. I haven't tempered yet because i was told that you should hand sand before tempering, will tempering possibly soften the scale too?
 
Warm vinegar will dissolve or loosen the scale, but it takes a while. If you are tempering in an oven with a good thermometer-go ahead and temper, then soak in vinegar.
 
The hotter the acid, the faster the scale removal. An even better option than vinegar is the "ph down" ("ph minus"?) powder that's used to lower the ph of swimming pools. You can find a tub of it on Amazon for around $15. I add a bunch of it to very hot water, and then put the blade in. All scale is removed within an hour or two. You can scrub and rinse the blade between soaks to help remove oil and residue.

Edited to add: you should ALWAYS temper your blades as soon as possible after hardening. When the blade has cooled to room temperature it's ready to go into the tempering oven. Never do any work on a blade that's been hardened but not tempered yet.
 
I primarily use 5160 and I have a bunch of scale all of the time. Vinegar works awesome to remove scale if you have a day or two. After two days of soaking most of the scale will either be floating in the vinegar or can be wiped off with a rag.
 
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