Aloha, fun & authoritative answers -- no cost, no passwords, no popups
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Metal finishing Q&As since 1989

-----

Bronze infiltrated 420 SS printed item needs de-rusting/de-scaling

May 18, 2018

Q. Hi all,
I would like some ideas on how to clean heat scale and rust from 420SS infiltrated with bronze(40%) please. The item in question is hollow so while I can scrub at the outside I don't have access to the inside of the item where it's also rusted etc(2mm holes). I tried using soap and citric acid bath separately but it didn't really work.

I thought about pickling the item in a nitric acid solution but that will etch the bronze, or maybe given a short enough bath maybe it won't be too bad I'm not sure. I can polish the outside with a rotary tool polishing stone but I no clue what to do for the inside.
Any ideas how to go about it?

Daniel Val
- Dublin, Ireland

A. I'd try Naval Jelly. Inexpensive, reasonably safe, does a good job of derusting, and leaves a light phosphate film to reduce future rusting.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
May 20, 2018

May 21, 2018

Q. Hi,
Thank you for your reply. I forgot to mention I'm looking to seal the remaining holes and electroplate the 420SS/Bronze after cleaning, will the phosphate film cause any issues with that?

The only way I can get Naval Jelly here is if I import it, will it be able to derust/descale small hollow areas without mechanical assist? Maybe an ultrasonic bath may help.

Update: I checked the data sheet of the Loctite compound and it says not for use on stainless steel, is this due to the phosphoric acid not passivating it?

I am open to electrolysis for rust removal, but will that also remove heat scale?

Regards,
Daniel

Daniel Val [returning]
- Dublin, Ireland

A. Daniel,
I would just use phosphoric or oxalic acid. Either will probably remove the rust faster than it will damage the brass.

Of course electroplating stainless usually requires something nasty like a Wood's nickel strike, which would render a moot point any less caustic acid used for precleaning.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

May 25, 2018

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: