Thread: Galvanising Rivited Rims

Your call, however here are some facts. Don't confuse Galv with Zinc Rich coatings or Annodes.



Zinc Rich Coatings Council Inc



Fact Sheet No 1 – August 2002




Features and benefits of zinc rich coatings systems



Are you a structural engineer, architect or steel fabricator in the process of selecting a corrosion protection system for an industrial or commercial project ? If so, there are ten questions you need to address before deciding on the best system. These questions are set out below together with answers which will guide you in making the right decision from both a performance and cost perspective.


Q. What is the life expectancy of zinc based coatings?
A. Both Hot Dip Galvanising and Inorganic Zinc Silicates can last 100 years or more in most rural environments.
Q. Is the high silicon content of some “cheap” imported steels a problem for zinc-based coatings?
A. Absolutely not. The chemistry of a steel substrate does not adversely impact on the protective coating applied. Accordingly the use of an inorganic zinc silicate coating as opposed to galvanising allows builders to maximise the benefits offered by the availability of low cost steel.

By contrast, during the galvanising process the high silicon/phosphorus content of cheap steels causes excessive zinc deposition. This leads to poor zinc adhesion, dull surface finish & colour variation and surface roughness. Galvanising thicknesses well in excess of 200 microns are not uncommon. This gives rise to flaking, peeling and brittleness thus reducing the quality and performance of a galvanised coating. Moreover the client could be asked to pay for the extra zinc deposited on the high silicon / phosphorous steel work.
Q. Can zinc based coatings be used for bolted connections ?
A. Only Inorganic Zinc Silicate coatings have the required coefficient of friction for bolted connections.
Q. Is steel distortion still a problem in the case of Hot Dip Galvanising?
A. Distortion of steel caused by Hot Dip Galvanising is a very real problem. For example, all beams galvanised for the Bunbury Bridge in Western Australia in 2000, distorted during the galvanising process.
Q. Are there any other problems associated with preparing the substrate for Hot Dip Galvanising or zinc rich coatings?
A. The pickling process often causes hydrogen enbrittlement in steel and precludes the use of affected steel from certain applications. Abrasive blast cleaning is the normal surface preparation for zinc rich coatings, which does not affect the steel in any way.
Q. What is “white rust”?
A. When newly galvanised surfaces are in prolonged contact with moisture they become affected by wet storage stains known as “white rust”. Specific storage conditions are required to prevent the occurrence of white rusting which can add to the cost of the project. Once white rust forms it is difficult and expensive to prepare the surface for painting, should this be a requirement. Even minor residues of white rust under paint inevitably lead to failure.
Q. What is the best way to compare the cost of different zinc based coatings?
A. When comparing costs do not fall into the trap of comparing apples with Mexican beans! The true way to compare costs is by comparing Hot Dip Galvanising with a single-coat Inorganic Zinc Silicate coating and not with a three-coat paint system.
The cost of painting large items is less than galvanising.
The cost of galvanising small items is less than painting.
Q. Is there any lead in Hot Dip Galvanising or Zinc Rich Coatings?
A. Traditionally there is a lead layer in galvanising baths, which protects the bottom of the bath from excessive heat and aids in the removal of Zinc Dross (a bi-product of the galvanising process). The lead is added to the bath either in ingot form or as an alloy such as “Prime Western” zinc metal. The lead is soluble (ie miscible) in molten zinc and results in the finished galvanised coating containing typically 0.5% - 0.9% lead. In contrast, the lead content of Zinc Rich Coatings is less than 1% of the metallic zinc content. The addition of lead to the galvanising process produces a finish known as “spangle”.
Q. Are there any Standards covering the amount of allowable defects in applied zinc based coatings?
A. Australian Standard AS/NZ 4680:1999 Hot-dip galvanised (zinc) coatings on fabricated ferrous articles allows individual defective galvanise film areas of up to 40cm2, in contrast with the 10cm2 maximum allowed in the International Standard on galvanising, ISO 1461:1999 Hot Dip Galvanised coatings on fabricated iron and steel articles -- Specifications and test methods. Contract specifications covering liquid coatings, including Zinc Rich Coatings, do not allow any defects in the applied films.
Q. Are there any health or environmental hazards associated with zinc based coatings?
A. Both water borne and solvent borne zinc rich coatings have a relatively low hazard associated with their application.
By contrasts, the galvanising process generates large volumes of hazardous fumes and waste materials. These include the sodium dichromate quench which contains Hexavalent Chrome 6, a known carcinogen. In Europe, the Stockholm City Council has banned the use of all galvanised products until an assessment of the hazards associated with the large volume of zinc present in the environment from man-made sources is completed.

Published by the Zinc Rich Coatings Council Inc
Freecall 1800 211 051 Fax (02) 9929-9743 Email zrcc@apmf.asn.au

For more information about zinc rich coatings, their uses and applications and to view detailed case studies visit our website at Zinc Rich Coatings Council ZRCC industry group for galvanising and zinc coatings

For professional technical advice contact the following suppliers of zinc rich coatings.

Akzo Nobel Pty Ltd (International Protective Coatings)
Phone: 131 474
Email: ipcmarketing@akzonobel.com.au
Ameron (Australia) Pty Ltd
Phone: 1300 659 666
Email: ern_hemmings@ameron.com.au
Jotun Australia Pty Ltd
Phone: (03) 9314-0722
Email: sales@jotun.com.au
Orica Protective Coatings (Dulux)
Phone: 132 377
Website: Dulux
Wattyl Australia Pty Ltd
Phone: (03) 9571-1095

Originally Posted by Tyrepower

Your call, however here are some facts. Don't confuse Galv with Zinc Rich coatings or Annodes.



Zinc Rich Coatings Council Inc



Fact Sheet No 1 – August 2002




Features and benefits of zinc rich coatings systems



Are you a structural engineer, architect or steel fabricator in the process of selecting a corrosion protection system for an industrial or commercial project ? If so, there are ten questions you need to address before deciding on the best system. These questions are set out below together with answers which will guide you in making the right decision from both a performance and cost perspective.


Q. What is the life expectancy of zinc based coatings?
A. Both Hot Dip Galvanising and Inorganic Zinc Silicates can last 100 years or more in most rural environments.
Q. Is the high silicon content of some “cheap” imported steels a problem for zinc-based coatings?
A. Absolutely not. The chemistry of a steel substrate does not adversely impact on the protective coating applied. Accordingly the use of an inorganic zinc silicate coating as opposed to galvanising allows builders to maximise the benefits offered by the availability of low cost steel.

By contrast, during the galvanising process the high silicon/phosphorus content of cheap steels causes excessive zinc deposition. This leads to poor zinc adhesion, dull surface finish & colour variation and surface roughness. Galvanising thicknesses well in excess of 200 microns are not uncommon. This gives rise to flaking, peeling and brittleness thus reducing the quality and performance of a galvanised coating. Moreover the client could be asked to pay for the extra zinc deposited on the high silicon / phosphorous steel work.
Q. Can zinc based coatings be used for bolted connections ?
A. Only Inorganic Zinc Silicate coatings have the required coefficient of friction for bolted connections.
Q. Is steel distortion still a problem in the case of Hot Dip Galvanising?
A. Distortion of steel caused by Hot Dip Galvanising is a very real problem. For example, all beams galvanised for the Bunbury Bridge in Western Australia in 2000, distorted during the galvanising process.
Q. Are there any other problems associated with preparing the substrate for Hot Dip Galvanising or zinc rich coatings?
A. The pickling process often causes hydrogen enbrittlement in steel and precludes the use of affected steel from certain applications. Abrasive blast cleaning is the normal surface preparation for zinc rich coatings, which does not affect the steel in any way.
Q. What is “white rust”?
A. When newly galvanised surfaces are in prolonged contact with moisture they become affected by wet storage stains known as “white rust”. Specific storage conditions are required to prevent the occurrence of white rusting which can add to the cost of the project. Once white rust forms it is difficult and expensive to prepare the surface for painting, should this be a requirement. Even minor residues of white rust under paint inevitably lead to failure.
Q. What is the best way to compare the cost of different zinc based coatings?
A. When comparing costs do not fall into the trap of comparing apples with Mexican beans! The true way to compare costs is by comparing Hot Dip Galvanising with a single-coat Inorganic Zinc Silicate coating and not with a three-coat paint system.
The cost of painting large items is less than galvanising.
The cost of galvanising small items is less than painting.
Q. Is there any lead in Hot Dip Galvanising or Zinc Rich Coatings?
A. Traditionally there is a lead layer in galvanising baths, which protects the bottom of the bath from excessive heat and aids in the removal of Zinc Dross (a bi-product of the galvanising process). The lead is added to the bath either in ingot form or as an alloy such as “Prime Western” zinc metal. The lead is soluble (ie miscible) in molten zinc and results in the finished galvanised coating containing typically 0.5% - 0.9% lead. In contrast, the lead content of Zinc Rich Coatings is less than 1% of the metallic zinc content. The addition of lead to the galvanising process produces a finish known as “spangle”.
Q. Are there any Standards covering the amount of allowable defects in applied zinc based coatings?
A. Australian Standard AS/NZ 4680:1999 Hot-dip galvanised (zinc) coatings on fabricated ferrous articles allows individual defective galvanise film areas of up to 40cm2, in contrast with the 10cm2 maximum allowed in the International Standard on galvanising, ISO 1461:1999 Hot Dip Galvanised coatings on fabricated iron and steel articles -- Specifications and test methods. Contract specifications covering liquid coatings, including Zinc Rich Coatings, do not allow any defects in the applied films.
Q. Are there any health or environmental hazards associated with zinc based coatings?
A. Both water borne and solvent borne zinc rich coatings have a relatively low hazard associated with their application.
By contrasts, the galvanising process generates large volumes of hazardous fumes and waste materials. These include the sodium dichromate quench which contains Hexavalent Chrome 6, a known carcinogen. In Europe, the Stockholm City Council has banned the use of all galvanised products until an assessment of the hazards associated with the large volume of zinc present in the environment from man-made sources is completed.

Published by the Zinc Rich Coatings Council Inc
Freecall 1800 211 051 Fax (02) 9929-9743 Email zrcc@apmf.asn.au

For more information about zinc rich coatings, their uses and applications and to view detailed case studies visit our website at Zinc Rich Coatings Council ZRCC industry group for galvanising and zinc coatings

For professional technical advice contact the following suppliers of zinc rich coatings.

Akzo Nobel Pty Ltd (International Protective Coatings)
Phone: 131 474
Email: ipcmarketing@akzonobel.com.au
Ameron (Australia) Pty Ltd
Phone: 1300 659 666
Email: ern_hemmings@ameron.com.au
Jotun Australia Pty Ltd
Phone: (03) 9314-0722
Email: sales@jotun.com.au
Orica Protective Coatings (Dulux)
Phone: 132 377
Website: Dulux
Wattyl Australia Pty Ltd
Phone: (03) 9571-1095

I have never read a more biased piece of drivel in my life (well maybe except for one of JohnF's posts). Facts... :lol

I have been using both gal and cold gal (zinc rich coatings) for many years. Cold gal is good, but in reality only a poor substitute for gal.