Cold Galvanising... Any good paints still available out there? 2

[CELinOttawa]

Hello All,

I've asked for Hot Dip Galv on a project, and the Contractor has asked if there are any paint options. I pointed out that I would only approve an alternative with the Owner's consent, but it seems that my old go-to products are no longer on the market.

Does anyone know of a good alternative to W.R.Meadows Galvafroid and Sherwin-Williams Zinc Clad 7? I'm told the new stuff is a mix of zinc and epoxy, but I just don't know if I'd trust that... The Sherwin rep told me of one of his suggestions "it is rated for a full year in contact with moist concrete.

I'm looking to embed the plate in grout/concrete/parging.

Thanks!

 

[cliff234]

ZRC Cold Galvanizing Compound

http://www.zrcworldwide.com/

 

[CELinOttawa]

Hello Cliff;

Looks like that's a great replacement to the paints I can no longer locate, only it has an added caution the others didn't which is going to be a problem for this particular job: "NOT RECOMMENDED FOR: Contact with potable water, strong acids or strong alkalis"

Concrete and grouts are strongly alkalyne when wet... I suppose I can always check with the manufacturer as to whether or not this is a problem.

Thanks!

 

[paddingtongreen]

I have worked with some of the best experts, and they were unanimous that there is no paint to equal hot dip galvanizing.

If you want to go with ZRC, look into covering it with an epoxy or other suitable coating to protect it from its environment. As in all coatings, the surface prep is the most important part of the process.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[hokie66]

Agree with Michael. In most environments, hot dipped galvanizing has superior longevity to even the best paint system. But maybe you worry too much...strong alkalinity protects the steel.

If you do go to a high performance coating other than HDG, inorganic zinc on a white metal blasted surface, followed by epoxy or urethane topcoats, is the usual regimen.

 

[dik]

HDG is still the best for Zinc stuff.... there are some zinc rich epoxies that can do the trick and one that I know of that can be used with slip critical faying surfaces... I'll dig up the name tomorrow...

Dik

 

[FEM4Structures]

ZRC GALVALITE
Read case studies for comparisons on ZRC WOrldwide

Thanks,

FEM4Structures

 

[hokie66]

The ZRC products are classified as organic zinc coatings (zinc in an epoxy carrier). They are undoubtedly fine products, but cannot provide the same degree of protection as hot dipped galvanising.

 

[cliff234]

Call the ZRC people and ask them your questions and express your concerns. I agree that hot dip galvanizing is best, but sometimes we need a different solution. The ZRC people have always given me straight answers to my questions.

 

[Ron]

Agree with others...HDG is better than any of the coatings. As hokie66 noted, surface prep is key to the success of any coating. Any of the zinc-rich coatings are going to be substandard to HDG....after all they are just coatings and cannot achieve the same ion exchange/galvanic corrosion protection of HDG...because their zinc particles are floating in an organic carrier, not metallurgically bound to the steel. ZRC is a good coating. Carboline/Tnemec Zinc Rich coatings are good as well.

If your plate is fully embedded in concrete, I wouldn't worry about a coating. If partially embedded in concrete, failure at the interface is inevitable....just a matter of time depending on HDG or coating.

 

[CELinOttawa]

Thank you all for your input. I want some zinc at least as this is being consealed behind a parting layer, so definitely cementitiuous but. Of properly concrete. I have warned the onwer and contractor that nothing will protect like HDG, but this is the way they want to go... I just want to make sure it is at least a reasonable level of sacrificial protection.

 

[Bagman2524]

My experience is also that there is no equal to hot dip galvanzied.

“Faith is taking the first step even when you don’t see the whole staircase.” MLK

 

[CELinOttawa]

Agreed; HDG is the real solution, with it performing flawlessly in many environments over a long track record.... When I was working bridge maintenance we Had historically required HDG followed by paint ten years later with five year intervals of maintenance touch-up coats on the high profile bridges. No rust, despite lots of salt used on our roads. In the 90s the maintenance budgets were cut, and shortly thereafter we started using replacement components that were only painted in a zinc-rich paint. That quickly resulted in rust, particularly for any bridge that really needed work in a budget-lean year.

Well aware that HDG is the best choice. With the owner not wanting the expense, I would been a techical or code based (read: defensible) position to refuse.

 

[dik]

These are the zinc related coatings from my General Notes... have a total of 43 different systems...

THE FOLLOWING COATING SYSTEMS SHALL BE USED:
SYSTEM 04: FAYING SURFACES (EPOXY TOPCOAT):
BASE METAL - STEEL
CLEANING - TO SSPC-SP 1 AND SSPC-SP 10
PRIMER - DEVOE 'CATHACOAT 302HB - REINF INORGANIC ZINC PRIMER'

SYSTEM 05: HOT DIPPED GALVANISING
BASE METAL - STEEL
CLEANING - TO SSPC-SP 1 AND SSPC-SP 10
HDG - TO ASTM A123, THICKNESS TO Z275

SYSTEM 09: EPOXY WITH ZINC RICH PRIMER
BASE METAL - STEEL
CLEANING - TO SSPC-SP 1 AND SSPC-SP 10
PRIMER - DEVOE 'CATHACOAT 302HB - REINF INORGANIC ZINC PRIMER
TOPCOAT - DEVOE 'BARRUST 235 - MULTIPURPOSE EPOXY COATING'

SYSTEM 10: EPOXY COATING OVER HDG
BASE METAL - HDG STEEL
CLEANING - TO SSPC-SP 1
WASH - POLYCLUTCH 97-687 BY PPG OR APPD EQ
PRIMER - AMERLOCK 400 TWO COMPONENT EPOXY BY PPG OR APPD EQ
TOPCOAT - AMERCOAT 450H TWO COMPONENT ALIPHATIC POLYURETHANE TOPCOAT BY PPG

SYSTEM 11: EPOXY COATING OVER HDG (ALTERNATIVE)
BASE METAL - HDG STEEL
CLEANING - TO SSPC-SP 1
PRIMER - DEVOE DEVRAN 201 EPOXY
TOPCOAT - DEVOE DEVTHANE 379 URETHANE

SYSTEM 12: THREE PART EPOXY COATING OVER HDG
BASE METAL - HDG STEEL
CLEANING - TO SSPC-SP 1
PRIMER - DEVOE DEVRAN 201 EPOXY
SUBCOAT - DEVOE 'BARRUST 235 - MULTIPURPOSE EPOXY COATING'
TOPCOAT - DEVOE 'DEVTHANE 379H - ALIPHATIC URETHANE GLOSS ENAMEL'

SYSTEM 23: POLYURETHANE COATING OVER HDG
BASE METAL - HDG STEEL
CLEANING - TO SSPC-SP 1
PRIMER - DEVOE DEVRAN 201H (POLYAMIDE EPOXY)
TOPCOAT - DEVOE DEVTHANE 379H (ALIPHATIC POLYURETHANE)


Dik

 

[CELinOttawa]

Thanks Dik; Very useful... Nice to have a reference for some replacement materials on hand.

 

[BAretired]

I used to spec a zinc rich paint called "Galvicon". Has it become obsolete?

BA

 

[TomDOT]

The hierarchy of protection goes something like this*:

Hot dip galvanizing
Sealed thermal spray
Inorganic zinc coating**
2=part/3-part Epoxy zinc coating***
Good one-component "cold galv" products
Cheap one-component products

*Presuming similar thickness, a quality product and proper application.
** With high time-of-wetness, high-ratio IOZ (like the original NASA formulation) can vault to the top of the list. Specific formulation matters, though.