Observations on Galvanic Corrosion Induced Paint Adhesion Loss

Roberts, Tracey; Kolts, J.; Steele, James H.

doi:10.4271/800443

Cited by 5 publications

(6 citation statements)

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“…The preceding discussion refers to coatings applied to a bare steel substrate. The presence of a chemical conversion coating improves durability, but the mechanism of failure is still complex (Holubka et al, 1980;Roberts et al, 1980;Watts, 1984b).…”

Section: Mechanisms Of Cathodic Disbondmentmentioning

confidence: 99%

Interface chemistry of stoved organic coatings

Castle¹,

Watts²

1985

Ind. Eng. Chem. Prod. Res. Dev.

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The failure, by mechanical delamination and by cathodic disbonding (both at rest potential and at cathodic polarization), of epoxy-phenolic, epoxy-acrylic, and styrenated alkyd coated mild steel has been characterized by X-ray photoelectron spectroscopy. In all cases failure occurs close to, but not at, the substrate/coating Interface. By matching the C 1s spectra to the sum of their components' peaks, It has proved possible to elucidate subtle differences In surface functionality. In the case of the epoxy resins, epoxy residues are displaced from the metal oxide surface by aqueous solution In accord with thermodynamic principles. The substrate and coating C 1s spectra following mechanical failure are, however, similar, as are those of the styrenated alkyd resin following corrosion-induced failure. These results are considered In the light of current theories of cathodic disbondment and other published data; it is concluded there is no universally applicable mechanism for this phenomenon.

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Section: Mechanisms Of Cathodic Disbondmentmentioning

confidence: 99%

Interface chemistry of stoved organic coatings

Castle¹,

Watts²

1985

Ind. Eng. Chem. Prod. Res. Dev.

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“…demonstrated that phosphorus was selectively removed from the phosphate coating when exposed to sodium hydroxide solutions. 2 Recently, Uchida and Deguchi, and Van Ooij and De Vries reported similar findings in commercial paint systems. 3.…”

Section: Introductionmentioning

confidence: 50%

“…A number of questions still needing answers are: 3 (1) Is the selective dissolution of phosphorus pH dependent? (2) Why is the phosphate ion more rapidly dissolved from the phosphate coating? (3) What effect do cations°S ubmitted for publication July 1986; revised January 1987.…”

Section: Introductionmentioning

confidence: 99%

“…published on the corrosion of steel in saline environments, and many corrosion reaction mechanisms have been proposed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Stern found that, in deaerated 4% NaCl over the pH range from 1 to 5, iron is -200 mV more active than the potential of the reversible hydrogen electrode in the same solution. Furthermore, sharp breaks dependent on pH were observed in cathodic polarization.…”

Section: Cknowledgments Introductionmentioning

confidence: 99%

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Effect of Alkali Metal Hydroxides on the Dissolution Behavior of a Zinc Phosphate Conversion Coating on Steel and Pertinence to Cathodic Delamination

Sommer

Leidheiser

1987

CORROSION

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Raman microprobe spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and wet chemical methods of analysis were successfully used to determine the effects of high-pH environments on zinc phosphate conversion coatings. The more rapid dissolution of phosphate ions from the phosphate coating was pH dependent. At a pH of 12.5, phosphate ions were more rapidly dissolved from the phosphate coating while at 11.5 and 13.5 pH, zinc ions were more rapidly dissolved from the coating. Raman spectra confirmed the more rapid dissolution of the phosphate ions was a result of zinc oxide formation on the surface of the original phosphate conversion coating. The cation of the alkaline environment also proved to be an important factor in the dissolution of the phosphate conversion coating. Sodium hydroxide dissolved the phosphate coating at the greatest rate followed by hydroxides of potassium, cesium, and lithium. This cation dependence was related to the number of precipitation products formed in the different alkaline solutions. AbstractAccelerated electrochemical techniques were used to study the corrosion of carbon steel in laboratory-simulated aqueous environments representing typical produced waters from natural gas production wells. Specifically, the separate and conjoint effects of the various ionic species in the electrolyte, and the influences of dissolved methane and propane on corrosion of the steel were investigated. Tests were performed at temperatures and pressures up to 95 C and 700 kPa, respectively. Some kinetic parameters were evaluated from both anodic and cathodic polarization measurements. The results showed that the reduction of H ZO and HCO3 -ions is important in explaining the cathodic polarization characteristics. The partial reactions occurring in the system were defined and explained, in part, from theoretical reconstruction of the experimental polarization curves.

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“…This has been discussed previously by Wiggle et al, 7 who, on investigating corrosion at scratches in paint films, reported that hydroxide produced by the cathodic corrosion reaction chemically dissolves the zinc phosphate, producing adhesion failure. Roberts et al 10 reported that there is a very strong dependence of the rate of removal of the phosphate coating with pH and has shown direct evidence that zinc phosphate degradation occurs by alkali attack. Further evidence that may support the argument for cathodic activity not only being responsible for the formation of initiation zones but also for the subsequent dissolution of phosphate conversion coating in adhesive bonds is that all interfacial failure has occurred within a narrow region around the edges of the failed interfaces.…”

Section: Analysis Of the Failure Interfaces Using Xps And Semmentioning

confidence: 99%