Home /
T.O.C.
FAQs
 
Good
Books
Ref.
Libr.
Advertise
Here
Help
Wanted
Current
Q&A's
Search 🔍
the Site

Problem? Solution? Chime right in!
(perhaps the world's last 'no registration' site)

-----

"How to remove rust from zinc plated steel without removing or damaging the zinc plating"



February 10, 2016

Q. Hello,

I'd like to find an efficient method for removing rust from zinc plated steel i.e. (bolts, screws brackets etc) without removing or damaging the zinc plating. I've tried using different kinds acids (phosphoric, hydrochloric, vinegar, CLR, in varying dilution ratios but the zinc is always destroyed. I was wondering about the process of chelation, where, if my understanding is correct, doesn't use acid to remove the rust. If chelation is a viable option, what is an efficient way to use this process.

thank you

mary

mary ross
car restorer - rochester, New York USA
^


February 10, 2016

A. The zinc was originally plated on the article to prevent it from rusting by sacrificial protection; in other words, zinc, being more active, will dissolve preferentially to protect the steel. And that's what happens when you put the article in any acid. If you're seeing red rust it means most of the zinc is already gone, having performed its' purpose. One option is to have the part replated; another is to strip the part of all coatings and apply zinc-rich paint, and a third option (often the most effective and least expensive) is to buy a replacement part.

tom_rochester
Tom Rochester Plating Systems & Technologies, Inc.  


supporting advertiser
CTO - Jackson, Michigan, USA

plating systems & technologies banner ad
^


simultaneous February 10, 2016

Q. Tom, thank you for responding to my question. I have a follow up question. I'm in the process of doing an experiment to see how quickly zinc plating will dissolve using three different diluted mild acids. Here are the acids I used: 1 pt white vinegar to 1 pt water, 1 part CLR to 1 pt water and 1 pt molasses to 10 pts water. I placed a zinc plated fastener (all the same) in each container. Here are the results so far:

Vinegar/water- zinc completely dissolved in 1 hour

CLR/water-zing dissolved completely in 15 minutes

molasses/water-no change in zinc 24 hours & counting

I just realized I didn't ask the follow up question that I referred to in my previous post. Here it is. I would like to be able to clean and remove any signs of red/brown rust from small zinc plated parts i.e. fasteners, brackets, clips, etc. and leave as much as possible of the zinc plating intact. Based on my experiment (last post) it appears that the molasses/water will accomplish this. Do you agree or would you recommend something different. Thank you for you assistance. It's much appreciated.

mary ross [returning]
- rochester, New York USA
^


February 11, 2016

A. Try 5 % ammonium citrate,ph 3,5 (dissolve 50 gms citric acid in 1 liter water,add ammonia until pH is 3,5!!!).

Hope it helps and good luck1

Goran Budija
- Zagreb,Croatia
^



February 19, 2016

Q. What about rust removal from the I.D. of tubing that has been zinc plated. The integrity of the plating itself on the O.D of the tube is fine. It is rusted on the I.D. because of the heavy stripping process in preparation for plating has attacked the raw I.D of the tube and thus rust. How do you remove that type of rust and not attack the plating on the exterior?

Russell Ahrens
- Sturgis, Michigan USA
^


March 2016

A. Hi Russell. I don't think you'll find any chemical or electrochemical way to remove rust without attacking the zinc plating. I think you will be limited to some sort of masking operation whereby whatever you do (sandblasting, acid dip, alkaline derusting) must be restricted to only the rusty bare steel inside of the tubing area.

In the future it may be possible to phosphatize and oil the inside of the tubing immediately after plating. That would be because the aggressive rust-removing acids would be applied before the zinc plating process. That is, the potential process might be: soak clean, electroclean, acid dip, zinc plate, chromate, phosphatize, oil (with rinses between each step).

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^

none
finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start 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:

 
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g, Train'g
& Software


About/Contact    -    Privacy Policy    -    ©1995-2021 finishing.com, Pine Beach, New Jersey, USA