Contact US

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!

*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

Dear Sir, I'm trying to passivate

Dear Sir, I'm trying to passivate

RE: Dear Sir, I'm trying to passivate

You can start by taking a look at the recommendations given by ASTM A380 and A967.

RE: Dear Sir, I'm trying to passivate

Buy a copy of A967 and read it.
10% nitric at RT isn't going to passivate (clean) properly.
303 can be problematic since it has such low corrosion resistance due to the deliberate inclusions.
If the white isn't visible to start with you can be assured that your solution has nothing to do with it other than making it obvious.
The variation in surface finish must be pre-existing.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Dear Sir, I'm trying to passivate

Hello isoca & Edstainless,
Thanks, For sharing your knowledgefull views.Actually, I have followed standard practice ASTM A380 only.Further i will take a look to A967 too as suggested by you.But, the thing is white marks (what's it exactly) is it frosting And I'm sure this white marks not present before Passivation. It's formed after passivation process.Is there any way to get this marks cleanout.
Note : Before Passivation there is machine oil present on the surface can it will be cause for thus marks & also are this marks are acceptable or it will cause any rejection.Please help me out.Thanks again

RE: Dear Sir, I'm trying to passivate

You should degrease (hot alkaline maybe) before passivation.
A straight nitric will not etch the surface, the condition must be pre-existing.
The passivation could be making it more visible but it wouldn't cause it.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Dear Sir, I'm trying to passivate

NOTE1. 303 SStl in any form is generally prohibited for use in MIL Acft due to cracking issues. I only know of 1-or-2 exceptions for parts... and there have been service bulletins for recurring inspections 'just-in-case'.

Per AMS2700... Method 1 passivation [conventional acid] treatments for all 303 CREs have somewhat unique passivation chemistry requirements... and the chemistries aren't even close to Your description.

Of course Method 2, citric acid chemistry seems to apply to most CR steels universally... but has it's own unique issues.

OH YES in every instance 'bath chemistry' must be strictly monitored/controlled, per ARP4992, Periodic Test Plan for Process Solutions. Where I work, there is a 'push' to method 2... simply because of general environmental, toxicity and disposal issues... but there is 'learning curve'.

Other info, 'good-to-know'.

AMS-STD-753 Corrosion-Resistant Steel Parts: Sampling, Inspection and Testing for Surface Passivation

When bath passivation is not possible... such as for field units [remote sites]... and passivation of 3xx SStl parts is required... then I have a 'field-fallback' I've used for years with moderate success... training and adhering to tech procedures per per USAF T.O. 1-1-691 is/are required for [A] and [B]. When is done/removed to expose clean bare-SStl the surface develops a natural/thin passivation film.

A. Apply PPG-Semco Pasa-Jell 101 to chemically 'clean/scrubbed [scotchbrite] surfaces and deburred edges'. This develops a thin passivation film 'good-enough' for epoxy primer adhesion in structural repairs. This is 'jelled-form' of phosphoric acid that is easier to control on small surfaces. https://res.cloudinary.com/engineering-com/image/upload/v1680273436/tips/PPG_Semco_Pasa-Jell_Gnrl_PDS_l7csh1.pdf

B. Another option is phosphoric acid cleaner per MIL-C-10578 Type III.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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