Bar Keeper's Friend Issue

[Cait_Sith]

I recently had some rust on some CPM M-4 steel and decided to use some Bar Keeper's Friend to try and remove it. Using a scotchbrite pad, I rubbed the BFK on the rust spots till they were gone and then rinsed the blade clean. When I dried off the blade, I found that it had heavily discolored and that more rust was already starting to form on the blade!

I know that BKF uses oxalic and citric acid to get rid of rust. But I didn't leave it on long and rinsed/dried it quickly. Is there anything I was doing wrong? And is there any better method to remove the rust?

 

[pjwoolw]

The scotchbrite pad is probably too aggressive for your task. A wine cork works well and won't make more places for rust to start. After using the BKF go over it again with baking soda. Dry and lubricate.

 

[Obsessed with Edges]

BKF's instructions also suggest wetting the surface with some water first, before applying the product to it. That'll moderate or dilute the oxalic acid's aggressiveness a bit, which is probably a good idea on carbon (non-stainless) steel especially. Might also help to mix the powder with some water first, to make a paste (which also dilutes it), then apply it sparingly to the wetted surface, as opposed to applying the dry powder directly onto the steel. Scrubbing with some baking soda afterwards, to help neutralize any acid left while rinsing, might also reduce the chance of further rusting.

BTW, baking soda can sometimes scrub rust off by itself, working as a mild abrasive which won't scratch the underlying steel. Red rust is softer and relatively loosely attached to the steel under it, so it often doesn't take much to scrub it off. I've used it to take rust off carbon blades after forcing a patina with vinegar. If a little more 'oomph' is needed, using the baking soda with some steel wool or a toothbrush or wire brush could also work. The steel wool & wire brush won't likely scratch the blade or alter it's finish, like a ScotchBrite pad can.


David

 

[D729]

Yes it's tricky. Steel is porous and you start a chemical reaction by using products that corrode, erode, rust things.
I have heard to never use products with bleach in them on "stainless" refrigerators. They don't stop rusting.
Baking soda is a great neutralizer. Thoroughly dry and keep coated with a product that prevents oxidation. It may become necessary to remove the damaged surface metal.

 

[Cait_Sith]

I've used the powder in the past, but saw that they had a liquid pre-mixed version so I tried that. Thanks for the advice, I think I'll got at it again by slightly diluting it.

 

[pjwoolw]

The liquid sucks. Don't waste your money.

Put a little powder some kind of small container. Add a bit of water until you make a paste. Wet the item your working on and scrub lightly in a circular motion with the cork or whatever. Always start with the cork and move up to something more abrasive if need be. Repeat process with baking soda. Or start off with baking soda and only use the BKF if you need to. This is the process I've used on more items that I can count for many years.

 

[Obsessed with Edges]

I've used the powder in the past, but saw that they had a liquid pre-mixed version so I tried that. Thanks for the advice, I think I'll got at it again by slightly diluting it.

I have a bottle of the liquid also, and it seemed to have lost a lot of it's punch over time (if it ever really had much to begin with; it's pretty weak stuff). The powder is what I keep going back to, and when used as a paste with some water, it has always impressed me. Do need to be careful with it, though.


David

 

[Stand Straight]

...
BTW, baking soda can sometimes scrub rust off by itself, working as a mild abrasive which won't scratch the underlying steel. Red rust is softer and relatively loosely attached to the steel under it, so it often doesn't take much to scrub it off. I've used it to take rust off carbon blades after forcing a patina with vinegar. If a little more 'oomph' is needed, using the baking soda with some steel wool or a toothbrush or wire brush could also work. The steel wool & wire brush won't likely scratch the blade or alter it's finish, like a ScotchBrite pad can.


David

That really surprises me. I would naturally suppose that steel wool and especially a wire brush would be items that you'd want to stay away from. I know steel wool comes in a variety of coarseness as wire brushes must also. ScotchBrite pads also have at least a couple different grit sizes. Good to know!
I sometimes use a strop to remove blems or other undesirable marks from blades, bolsters, etc.

 

[Obsessed with Edges]

That really surprises me. I would naturally suppose that steel wool and especially a wire brush would be items that you'd want to stay away from. I know steel wool comes in a variety of coarseness as wire brushes must also. ScotchBrite pads also have at least a couple different grit sizes. Good to know!
I sometimes use a strop to remove blems or other undesirable marks from blades, bolsters, etc.

The bristles of wire brushes, as well as steel wool, usually won't be hard enough to scratch hardened cutlery steel. If still in doubt, a brass-bristled brush would pose even less risk, used on a steel blade. ScotchBrite pads utilize aluminum oxide abrasive grit impregnated into the pad, which is a lot harder and much more likely to alter a steel blade's finish.


David