No registration or passwords; no pop-up ads -- just aloha, fun, & answers.
(as an eBay Partner & Amazon Affiliate earns from qualifying purchases).
Home /
T.O.C.
Fun
FAQs
Good
Books
Ref.
Libr.
Advertise
 
Help
Wanted
Current
Q&A's
Site 🔍
Search
pub  Where the
world gathers for metal finishing
Q&As since 1989



-----

Powder coating pre treatment process after galvanizing




Dear Sir,

I have to powdercoat a steel section of 6mm thick after hot dip galvanizing. After Gal process I do not do water or chromate quenching and within 24 hrs I do the powder coating (Pure polyester) and I want the coat to withstand 1000 hrs salt spray. PL guide me to the pre treatment process I should go for before powder coating. I hv been confused by a lot of people please inform me the correct method.

Venky
Steel section manufacturer - Chennai, TN, India
2004



First of two simultaneous responses -- 2004

Dear Sir.,

We have used the following process for a long time with no problem and a good performance.

1. Alkali degreasing
2. Rinse Water
3. Pre phosphate rinse
4. Zinc Phosphate
5. Phosphate rinse
6. Sealer.

To guarantee that you will get 1000 hours will depend on the chemistry that you use in your plant, and the control that you take on the pre treatment stages.

I will recommend you to read a couple of good articles on this on the following web sites: https://www.galvanizeit.org/showContent,178,220.cfm#profiling http://www.corp.indgalv.com.au/technical/powcoat.htm

As you will find from the readings the use of Zinc Phosphate will perform best.

Juan Carlos Sanin
- Medellin, Colombia



Second of two simultaneous responses -- 2004

There are only really three pretreatments for powder coating galva steel. 1. Light shotblasting. Re-profiles the surface to allow adhesion to the zinc, but has disadvantage of removing quite a lot of zinc, and if human dependent on how much is removed. 2. Zinc phosphate preceded by degreasing, and acid etching with plenty of rinsing in between. 3. Chromate also with degreasing, acid etching and lots of rinsing.

Galv needs to be etched (or re-profiled) to get adhesion, but the zinc phosphate is best in my opinion. We get 2000 hrs with this.

geoff_crowley
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
crithwood logo




(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:

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


About/Contact  -  Privacy Policy  -  ©1995-2024 finishing.com, Pine Beach, New Jersey, USA  -  about "affil links"