nitric acid to passivate

Karl:

You've got to check shipping. I understand some strengths can't be shipped by air, and they might not ship to private parties.

Citric acid is used in cooking/baking. The local supermarket in Washington State had citric acid in the bulk food department. But you will probably only find it in a really large supermarket.

Check Ernie Leimkuhler's website or search in SEJW. Ernie uses a citric acid sold for passivation.

Dan

Welding supply stores. Nitric acid is better. Steve

Nitric acid passivation is probably better (it also removes some scale and discoloration, too) but citric acid does pretty well. I use 8-10% by volume citric acid in distilled water for at least an hour at 150 F with agitation. Should be longer than necessary but time is cheap in this case. I've done comparisons using small pieces of 304 16 ga sheet with tig beads run in one direction and then cut up into strips so each strip had 2 or 3 beads across it, and the citric makes a big difference compared to nothing. Glass beading first helps slightly but of course gets rid of all the bluing. Glass bead or not, passivate or not, bake at 450 F for an hour or not, then submerge in concentrated salt water for a few days and look for rust. All three is best. McMaster Carr sells citric acid.

----- Regards, Carl Ijames

I get my citric acid in the local pharmacy.

I did also as a kid with soda rockets.

Guess they would do it for a person - a buck is a buck. Customer is gold.

Mart>> I need some nitric acid to passivate some stainless. Anybody know of a

It's available in the Twin Cities but I don't know where. Mary's Dad's business in St. Paul did stainless passivation. I still have a gallon jug of fuming HNO3 but I'm not sharing!

Note that since nitric acid is a primary substance used in making nitroglycerine and other similar explosives, it is probably rather tightly controlled and tracked these days.

Enjoy, DoN.

I get both from a mail-order chemical supply here in the UK. I can't think of any "domestic" preparations that would be mainly nitric acid. But the stuff's so useful when you do need it that it's worth a little trouble to get a supply.

Mark Rand RTFM

Nitrates are used in explosives. So, it's unlikely you'll find a source of nitric acid.

As no one has so far mentioned it, ill do so. Nitric acid is used regularly in electroplating works. If youve one near you, look in your yellow pages under plating, they may do passivation anyway, or let you have enough to do what you want.

im in the UK as well, and have no problemsgetting the stuff from Canning. Birmingham. I do collect it tho on prior order.. whatsa abit more difficult to get is the real nasty, Hydroflouric acid. Nitric is the basis constituent of bright dip. Great stuff for cleaning corrosion off non ferous copper based alloys.

hope this helps.

Yes, if you set up a new account and try to order strong oxidizers, I would expect some penetrating questions. If you have a long-term existing business with a legitimate need, it shouldn't be a serious problem.. but it might cause delays. BTW, concentrated nitric acid will attract Hazmat shipping fees (ground shipping only). I would expect individuals would not be able to easily buy such chemicals.

We use a lab supply house for reagent grade chemicals, but they tend to be a bit expensive.

Unless my memory is failing, to passivate stainless with nitric acid, you have to get it hot, correct? I thought that's why people used hydrofluoric acid for small-batch passivating. Hot nitric is very nasty stuff.

And cold HF is even nastier.

But isn't it safer to handle, at least because of the cooler temperature? And how about the fumes? I don't know the answers to these questions; I'm just asking.

The only hydrofluoric I've been near is the pasty stuff that comes in a tube, which you can get at your local welding supply. But I only needed a dab of it.

I'm OK with fuming HNO3 but I wouldn't mess with HF outside of a properly-equipped lab. Quote from Wikipedia:

The danger in handling hydrofluoric acid is extreme, as skin saturation with the acid in areas of only 25 square inches (160 cm2) may be relatively painless, yet ultimately fatal. High concentrations of hydrofluoric acid and hydrogen fluoride gas will also quickly destroy the corneas of the eyes.

I was going to tell him this and decided to see if someone beat me to to it. :-) ...lew...

Ugh. I'm glad I don't have to passivate any stainless.

Aside from trying to clean up a weld with the hydrofluoric paste (it didn't do the job very well; it got rid of the blue, but there was still black oxide left on the weld), my limited experience with nitric was in etching mold surfaces. We had a very powerful hood for that, but I refused to do it indoors, anyway.

HF you don't even want to be in the same zip code with - it gets in your system and just keeps destroying.

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