Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Need help understanding this formula

Need help understanding this formula

Need help understanding this formula

"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!

Here is more info

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

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

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.

RE: Need help understanding this formula

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

RE: Need help understanding this formula


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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


White Paper: Industrial Control Basics: Contactors
A contactor is an electrical device used for switching an electrical circuit on or off. Considered to be a special type of relay, contactors are used in applications with higher current carrying capacity, while relays are used for lower current applications. Download Now
Research Report: State of IoT Adoption in Product Development 2019
This research report, based on a survey of 234 product development professionals, examines the current state of Internet of Things (IoT) adoption by product design teams, its perceived importance, and what features and capabilities teams consider important when making decision about adding IoT functionality to their products. Download Now
Research Report: Augmented Reality for Maintenance, Repair and Overhaul (MRO)
The term Industry 4.0 denotes a cluster of technologies that’s poised to fundamentally reshape manufacturing and bring about a new industrial revolution. These include 3D printing (AM), the Industrial Internet of Things (IIoT), artificial intelligence (AI) and mixed reality technologies, more commonly known as virtual reality (VR) and augmented reality (AR). Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close