What does the cold galvanizing process consist of?
The term cold galvanizing is more of a marketing term than an actual process. Cold galvanizing is simply painting a piece of steel with zinc-rich paint. There are not tanks or preparation necessary other than the equipment you would need to paint any other material (blasting tools, spray guns or rollers, etc.). Because the coating is simply zinc-rich paint, it will not have the durability of hot-dip galvanizing in terms of abrasion resistance, cathodic protection, and service life (or time to first maintenance). The cathodic protection offered by zinc-rich paint is less than hot-dip galvanizing because there are binders and other elements in the paint which limit connectivity of the zinc particles.
© 2023 American Galvanizers Association. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.
Comments
Octavian Breazu
Can the Rust-Oleum Cold Galvanizing Compound spray pain be top coated with car paint? I had a small surface in the front of the car where rust came up in many spots and kept coming, no matter what treatment I've used. Lately, I've found the cold galvanizing paints and decided to give it a try in that area. My plan was to apply several layers of zinc rich paint and then repaint with the original color. I consider it as a primer but I have a mixed feeling now. The manufacturer says "No top coat required" but this does not mean it cannot be top painted. Any idea? Thank you, Octavian
(AGA)
Octavian, Zinc rich paint is often top coated or it can be used alone. However, you will need to contact the manufacturer of the zinc rich paint to determine compatibility with the paint you wish to top coat it with and follow the manufacturer instructions regarding this process.
Sharanabasava
Cold galv. means, steel need to be galvanized with spray after erection in site? Please let me know the confusion.
(AGA)
Sharanabasava, Cold galvanizing is zinc rich paint (spray or brush) which can be applied either in the shop or in the field.
(AGA)
Sharanabasava, Cold galvanizing is zinc rich paint (spray or brush) which can be applied either in the shop or in the field.
Dianna Hudec
Hello. Will cold galvinizing paint work on jewelry? Will it be durable enough? Thank you.
(AGA)
Hi Dianna, you can expect a similar level of durability as other industrial paints. Contact the paint manufacturer for more detailed information including durability against cleaning, etc.
Jan Konigsberg
I am rehabilitating my Endless Pool which has galvanized sheet metal walls for structural support and a vinyl liner that holds the water. The pool is about 17 years old and condensation between the vinyl liner and metal wall as well as leaking through the vinyl caused white rust and red rust. When I scrape off the white rust (oxidation of the zinc as I understand it), the metal is a medium dark gray in color; so, I am wondering if that coloration indicates the metal still is sufficiently galvanized or whether I have to re-galvanize with cold galvanizing compound. The metal under the red rust will have to be re-galvanized. I am also wondering if the can of spray-on Rustoleum cold galvanizing compound is a better choice or not than painting from the 1 quart can of Rustoleum cold galvanizing compound. Thanks in advance for your answers to these questions.
(AGA)
Hello Jan, A coating thickness gauge can be used on the dark metallic areas to determine whether galvanized coating remains, or reads near 0 (bare). Zinc-rich paints used for repair of hot-dip galvanizing must contain either between 65% to 69% metallic zinc by weight or greater than 92% metallic zinc by weight in dry film. Apply in accordance with the manufacturer's instructions.
James Smith
We have to replace our 30 year old wooden private power pole with a H.D. Galvanised 4.5mm thick steel pole due to site constraints. I found your article as I was researching whether I could proactively increase its service life by applying a zinc coating before our electrician installs it. From what I’ve read there would be no real advantage to doing this. Please correct me if I am wrong. Also, is the use of quick setting concrete likely to exacerbate corrosion more so than standard concrete or using a tampered blue metal base? Grateful for any advice
(AGA)
Hi James, Correct, the hot-dip galvanized coating already provides protection from corrosion. Reactions between galvanized steel and concrete are only of concern during the initial curing stages of the concrete (when still wet). As this is a relatively short time, attack on the galvanizing will be typically negligible.
Mike La
We live in a very foggy hillside and had to replace our deck due to rusted brackets and other issues. Contractor used non galvanized column cap/brackets on the new treated wood deck. Is it of any use to spray or paint on cold galvanizing paint onto these brackets on the deck now? Will there be even more increased corrosion where paint touches the treated wood? Thanks for any advice.
(AGA)
Hello Mike, Only hot-dip galvanized steel and stainless steel are recommended for long term use with pressure treated wood. Painting the outer face of the bracket will not protect the steel from the pressure treated wood directly in contact beneath the bracket.
Dan Biagini
Hi Mike, Does cold galvanizing compound ( rustoleum) etch into rusted and nonrusted galvy to prep for POR-15 products.
(AGA)
Hi Dan, contact the POR Products Inc. (product manufacturer) to discuss compatibility with their product over the specific zinc-rich paint product you are using for galvanizing repairs.
[Comment awaiting moderation]
Gordon Fitch
I am dealing with an old roof that seems to be galvanized steel (or possibly iron). Most of the zinc coating is still in place. I am experimenting with a supposedly high-density zinc paint (Rustoleaum). It seems possible that the paint's zinc particles will have some conductance through the existing zinc, but others argue against this. What do you think?
(AGA)
Hi Gordon, Zinc-rich paints only improve aesthetics and increase barrier protection for areas with a sufficient zinc coating. Areas with depleted or compromised zinc coatings will also benefit from cathodic protection provided by the zinc in the paint. See our Dr Galv article- Touch Up and Repair for more information on repairing HSG steel to ASTM A780.