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(Coating Formulation) Coatings on the Edge of Forever

Picture for Coatings + Proceedings 2021-ALL Papers
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A continuing problem with coatings applied to sharp edges of a structure is the corrosion that often develops at the apex of the edge. The conventional wisdom is that the reduction of film thickness, due to coating pulling away at the edge during the curing of the coating, is the primary cause for the onset of corrosion. This theory, however, is not necessarily correct, both from a mechanistic and practical point of view.

Product Number: 12-COAT_DEC21
Author: Carl Reed / Kat Coronado
Publication Date: 2021
Industry: Coatings
$0.00
$20.00
$20.00

A continuing problem with coatings applied to sharp edges of a structure is the corrosion that often develops at the apex of the edge. The conventional wisdom is that the reduction of film thickness, due to coating pulling away at the edge during the curing of the coating, is the primary cause for the onset of corrosion. This theory, however, is not necessarily correct, both from a mechanistic and practical point of view. This discussion paper will present the conventional viewpoint of what is called “edge retention” or “edge coverage” and why it is insufficient in describing corrosion occurrence at an edge. Also discussed is how the current test methods provide non-relevant data to edge coverage observations.
A different mechanism of the causation of corrosion at an edge is presented as well as an alternative method for evaluating the effect of edge coverage on corrosion of the system.

A continuing problem with coatings applied to sharp edges of a structure is the corrosion that often develops at the apex of the edge. The conventional wisdom is that the reduction of film thickness, due to coating pulling away at the edge during the curing of the coating, is the primary cause for the onset of corrosion. This theory, however, is not necessarily correct, both from a mechanistic and practical point of view. This discussion paper will present the conventional viewpoint of what is called “edge retention” or “edge coverage” and why it is insufficient in describing corrosion occurrence at an edge. Also discussed is how the current test methods provide non-relevant data to edge coverage observations.
A different mechanism of the causation of corrosion at an edge is presented as well as an alternative method for evaluating the effect of edge coverage on corrosion of the system.

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Picture for Coatings + Proceedings 2021-ALL Papers
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(Coating Formulation) Can Low Zinc Epoxy Primers Work as Well as Traditional Zinc Rich Epoxy Primers

Product Number: 47-COAT_DEC21
Author: Alex Yagüe / Pinturas Hempel / David Morton
Publication Date: 2021
$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.
Picture for Coatings + Proceedings 2021-ALL Papers
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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.
Picture for Coatings + Proceedings 2021-ALL Papers
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(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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