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# Need help understanding this formula3

## Need help understanding this formula

(OP)
"Mixture of 50% v/v nitric acid + 20-25% v/v sulfuric acid + 1-2 lb/gal ammonium bifluoride, balance water to 100%."

It is a tri-acid solution for desmutting/deoxitsizing die cast aluminum allow (383) before chromate conversion coating.

Can anyone walk me through the formula plz! Thanks!

### RE: Need help understanding this formula

Figure out how much solution you need in gallons. Assume you need 1 gallon. then you'd have 0.5 gallon of nitric acid (conc = ?),up to 0.25 gallon of sulfuric acid (conc = ?), up to 2 lbs of ammonium bifluoride, and approximately 0.25 gallons of water. The formulation doesn't specify the concentration of the acids, which confuses me. You can use the concentrated versions available for purchase, if you have the proper chemical handling equipment (PPE, fume hood, etc.)

### RE: Need help understanding this formula

(OP)
jari001, Thanks for breaking it down!

Another question, if you don't mind...What would be the proper mixing steps to make a bath?
I am looking up the concentration.

### RE: Need help understanding this formula

Think back to chemistry class, add acid to water never the other way around.
Heating will be a serious issue when mixing this.
If it were me I would start by adding the sulfuric to the water, then adding the nitric, and then the Fl last.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Need help understanding this formula

I agree with EdStainless.

You'll want to have a proper vessel that can hold this acidic solution (sturdy plastic or glassware); it's also going to be deceptively heavy so plan how you will transport it if you make large quantities at once. Start with the water and slowly add acid; you don't have to dribble it in mL by mL but don't just dump the full amount in one go. If you use concentrated sulphuric and nitric acid, they will be viscous so you might require a mixing aid. This bit could be a bit tricky if you are going to make multiple gallons of the stuff at once, but if it's beaker scale then some medium or large stir bars will do the trick.

I know this is obvious, but it bears repeating, this solution should be considered and treated as corrosive and toxic. I would consider proper ventilation, faceshield/goggles, nitrile or rubber gloves, lab coat/apron, long sleeves, and closed toes shoes the minimum safety precautions. Your company's safety policy may be more stringent.

### RE: Need help understanding this formula

I wouldn't use glass, the Fl will etch it.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Need help understanding this formula

@EdStainless
Yes, that's a good precaution to take since the prep vessel may serve as the bath vessel for whatever gets this finishing treatment. I missed that.

(OP)
Thanks guys!

### RE: Need help understanding this formula

And I shouldn't need to say this, but this mixing will require the highest level of PPE that you can get, goggles, respirator, full face mask, acid proof coat and gloves. This is serious stuff.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

(OP)
EdStainless,

Of Course

### RE: Need help understanding this formula

Naw! This is your opportunity to use that old holely Hard Rock tee shirt and those flipflops you haven't gotten your money worth of yet.

Keith Cress
kcress - http://www.flaminsystems.com

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