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(Coating Formulation) Can Low Zinc Epoxy Primers Work as Well as Traditional Zinc Rich Epoxy Primers

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Zinc-rich primers, with zinc dust loadings of 80-85% by weight in the dry film, are often the preferred primer during new construction of assets placed in environments with high atmospheric corrosivity. Coating standards such as SSPC-Paint 20 and ISO 12944 demand that zinc-rich primers contain at least 65% and 80% zinc dust by weight in the final dry film, respectively. Traditional zinc rich primers need this high zinc loading to achieve galvanic protection of steel. New technology allows us to develop zinc primers with a lower content of zinc and/or different zinc morphology than dust to provide similar or better corrosion protection to the steel.

Product Number: 47-COAT_DEC21
Author: Alex Yagüe / Pinturas Hempel / David Morton
Publication Date: 2021
Industry: Coatings
$0.00
$20.00
$20.00

Zinc-rich primers, with zinc dust loadings of 80-85% by weight in the dry film, are often the preferred primer during new construction of assets placed in environments with high atmospheric corrosivity. Coating standards such as SSPC-Paint 20 and ISO 12944 demand that zinc-rich primers contain at least 65% and 80% zinc dust by weight in the final dry film, respectively. Traditional zinc rich primers need this high zinc loading to achieve galvanic protection of steel. New technology allows us to develop zinc primers with a lower content of zinc and/or different zinc morphology than dust to provide similar or better corrosion protection to the steel.
Previous studies on traditional zinc-rich epoxies showed that only the zinc in the first 20-30 microns (0,79-1,18 mils) of the coating can provide galvanic protection. As a normal zinc coating is specified typically at 60-80 microns (2,36-3,15 mils) most of the zinc is not able to protect the steel against corrosion. A new zinc activation technology not only improves the cathodic protection of zinc-rich epoxies but also enables us to decrease, significantly, the zinc content in the dry film without compromising the anticorrosion properties of the primer. Additionally, the synergistic combination of the activation technology and zinc flakes allows the formulation of epoxy primers with reduced content of zinc which exhibit excellent corrosion protection to the steel.
This paper will examine the formulation of new activated low zinc epoxy primers and compare their mechanical and anticorrosion properties to conventional zinc rich epoxy primers. Comparable corrosion resistance at reduced zinc levels in the dried film will be demonstrated and show that zinc metal levels can be reduced to as low as 45% by weight without compromising galvanic protection while improving adhesion and mechanical properties of the dry film. Finally, the performance in cyclic ageing test of the primer in a two-coat system will also be presented.
Learning objectives
• Amount of zinc can be reduced in zinc primers
• New ways of formulating zinc primers will be discussed
• Levels of corrosion protection can be maintained with excellent mechanical properties
• Anti-corrosive performance of low zinc primer in a two-coat system

Zinc-rich primers, with zinc dust loadings of 80-85% by weight in the dry film, are often the preferred primer during new construction of assets placed in environments with high atmospheric corrosivity. Coating standards such as SSPC-Paint 20 and ISO 12944 demand that zinc-rich primers contain at least 65% and 80% zinc dust by weight in the final dry film, respectively. Traditional zinc rich primers need this high zinc loading to achieve galvanic protection of steel. New technology allows us to develop zinc primers with a lower content of zinc and/or different zinc morphology than dust to provide similar or better corrosion protection to the steel.
Previous studies on traditional zinc-rich epoxies showed that only the zinc in the first 20-30 microns (0,79-1,18 mils) of the coating can provide galvanic protection. As a normal zinc coating is specified typically at 60-80 microns (2,36-3,15 mils) most of the zinc is not able to protect the steel against corrosion. A new zinc activation technology not only improves the cathodic protection of zinc-rich epoxies but also enables us to decrease, significantly, the zinc content in the dry film without compromising the anticorrosion properties of the primer. Additionally, the synergistic combination of the activation technology and zinc flakes allows the formulation of epoxy primers with reduced content of zinc which exhibit excellent corrosion protection to the steel.
This paper will examine the formulation of new activated low zinc epoxy primers and compare their mechanical and anticorrosion properties to conventional zinc rich epoxy primers. Comparable corrosion resistance at reduced zinc levels in the dried film will be demonstrated and show that zinc metal levels can be reduced to as low as 45% by weight without compromising galvanic protection while improving adhesion and mechanical properties of the dry film. Finally, the performance in cyclic ageing test of the primer in a two-coat system will also be presented.
Learning objectives
• Amount of zinc can be reduced in zinc primers
• New ways of formulating zinc primers will be discussed
• Levels of corrosion protection can be maintained with excellent mechanical properties
• Anti-corrosive performance of low zinc primer in a two-coat system

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(Coating Formulation) Corrosion Resistance Comparison of Zinc-Rich Epoxy With Reduced Zinc Levels

Product Number: 46-COAT_DEC21
Author: Mary Roley
Publication Date: 2021
$20.00

Zinc-rich coatings have long been known to provide excellent corrosion resistance in highly corrosive environments, in general,inorganic zincs for new construction and organic zincs for maintenance. A recent trend has been toward zinc-rich coatings with reduced levels of zinc dust. An SSPC committee formed to revise SSPC Paint 29, Zinc Dust Sacrificial Primer, Performance Based, to reference performance only, removing reference to minimum zinc dust level.
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Product Number: 15-COAT_DEC21
Author: William D. Corbett
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The use of duplex coating systems (hot dip galvanizing or thermal spray coating with one or more liquid-applied coatings) for long term protection of structural steel is becoming more mainstream in many industries. This paper describes the advantages of employing duplex coating systems as well as some important considerations for designers prior to specifying their use. It also highlights an ongoing initiative to help agencies more efficiently and effectively use duplex coatings on steel bridges by developing guidelines, standards, and other materials.
Picture for Coatings + Proceedings 2021-ALL Papers
Available for download

(Coating Formulation) Efficacy of Zinc Content in Sacrificial Protection of Coatings

Product Number: 44-COAT_DEC21
Author: Nicole Rakers / Mary Lyn Lim / Michael McCarthy / James Begley
Publication Date: 2021
$20.00

Zinc rich coatings have long been used in the protective coatings industry as one of the primary means of steel substrate protection against corrosion. The primary protection mechanism has historically been galvanic sacrificial loss of zinc metal and the simultaneous formation of protective zinc oxides and salts. Various standards and customer specifications exist to ensure that the coating will provide the necessary corrosion protection for the life of the asset.
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