Special Applications of Cathodic Protection - Stainless steel, Aluminium Alloys and Unusual Geometries

Peterson, M. H.; Lennox, T. J.; Groover, R. E.

doi:10.4043/1462-ms

Cited by 3 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus in crevices not coupled to outside open metal, when the crevice height is comparable to the thickness of the oxygen diffusion layer, diffusion of oxygen into the crevice is impeded and hence the corrosion rate is reduced, according to Eq. [2].…”

Section: Inhibitor-free Solutionsmentioning

confidence: 99%

See 1 more Smart Citation

Electrochemical Behavior of Iron Within Crevices in Nearly Neutral Chloride Solutions

McCafferty¹

1974

J. Electrochem. Soc.

View full text Add to dashboard Cite

In crevices where the internal iron is not short-circuited to external metal, the corrosion rate is determined by the limiting cathodic current for oxygen reduction. This limiting current, and accordingly the corrosion rate, is independent of pH and C1-concentration but is suppressed to a constant value when the height of the crevice is less than the thickness of the oxygen diffusion layer. When iron in the crevice is short-circuited to external, open platinum, the initial crevice corrosion rate is independent of crevice height but increases with increasing C1-concentration and area of external electrode. At constant CI-concentration, the crevice corrosion rate of internal iron short-circuited to o~en external iron decreases with increasing chromate ion concentration. At a constant chromate ion concentration which does not give protection, the crevice corrosion rate is greater the greater the chloride ion concentration for short times, but at longer times the rates are essentially independent of bulk chloride concentration.Rosenfeld and Marshakov (1) have shown that crevice corrosion usually proceeds in two main stages: (i) initiation by differential aeration and (ii) propagation by crevice acidification. Initially, the sheltered metal in contact with a restricted oxygen supply becomes anodic relative to the open metal to which it is connected. At longer times, the presence of the crevice plays a different role, that of causing corrosion products to accumulate within the crevice so as to change the local solution composition and pH.Reports that not only crevices (1, 2) but also stresscorrosion cracks (3, 4) and pits (5, 6) acidify locally has led to the view that all three forms of localized corrosion share the unifying feature of being "occluded corrosion cells" (7) having restricted exchange with bulk electrolyte and thus common solution chemistries. Thus, most recent studies have utilized the thermodynamic, rather than kinetic, approach, with emphasis on factors such as resultant crevice solution chemistry, pH, and electrode potential (8-11). Little recent work has been done on the polarization kinetics of metals under crevices. One exception has been the correlation between the shape of cyclic anodic polarization curves for various engineering alloys in 3 89 % NaC1 with their longer range performances in natural seawater (12). Polarization curves have been reported in some well-defined but synthetic, generalized "occluded corrosion cells" sans crevices, in which the "internal" metal was activated by anodic polarization (13) or by deaeration (14). Other investigators have reported current-time (15) and potential-time (10, 16), but not current-potential relationships.The purpose of this study was to take up the systematic approach of Rosenfeld and Marshakov (1) in order to investigate in an organized manner kinetic aspects of a fairly simple crevice system. Iron was chosen, partly because of the attention given this metal in a wide variety of open systems. The effect of vari-* Electrochemical Society Active Mem...

show abstract

Section: Inhibitor-free Solutionsmentioning

confidence: 99%

“…An accumulation of ferrous ions within the crevice has been found (2,12) to accompany the low pH. Possible equilibrium reactions leading to an increase locally in H + ions involve the hydrolysis of ferrous ions entrapped within the crevice, and have been summarized by Peterson (2).…”

Section: August I974mentioning

confidence: 99%

Electrochemical Behavior of Iron Within Crevices in Nearly Neutral Chloride Solutions

McCafferty¹

1974

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…According to Pourbaix's model, the internal electrolyte within such "occluded corrosion cells" ( 9) is a saturated ferrous chloride solution, in equilibrium with the solid corrosion products Fe304 and FeCl2 9 4H~O. A number of experimental studies, mostly with stainless steels, have confirmed that occluded cell electrolytes become concentrated in metallic cations and in chloride ions (10)(11)(12)(13)(14)(15). Recent thermodynamic calculations taking activity coefficients into account (16) have verified that at equilibrium, the internal electrolyte in the case of pure iron is saturated solution of ferrous chloride.…”

mentioning

confidence: 99%

Calculation of the Free Energy of Formation of Ferrous Chloride Tetrahydrate

McCafferty

1984

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

Long term corrosion behavior of clad aluminum materials under different atmospheric conditions

Poltavtseva

Heyn

Boese

2013

Materials & Corrosion

View full text Add to dashboard Cite

Aluminum materials roll‐plated on both sides are combinations of metals, which consist of clad layers on a core. To document the long term behavior of roof profiles of Alclad 3004 after long term exposure of about 40 years, evaluations were made at three locations in Germany with different climatic conditions. Locations with typical rural‐urban, coastal‐urban, and industrial climates were selected. The corrosion progress as a function of time and climatic type could be characterized by cross‐sections of roof specimens. To interpret the protective mechanism of the clad layer, the corrosion behavior of Alclad 6025 was characterized by electrochemical investigations. The results show that the passive clad material easily undergoes pitting in media containing specific amounts of chlorides. In case of contact of both cladding and core with an electrolyte the core alloy was protected because of the pitting corrosion of the cladding. This guarantees long‐time corrosion protection of constructions like facades or roofs under different atmospheric conditions.

show abstract

Special Applications of Cathodic Protection - Stainless steel, Aluminium Alloys and Unusual Geometries

Cited by 3 publications

References 0 publications

Electrochemical Behavior of Iron Within Crevices in Nearly Neutral Chloride Solutions

Electrochemical Behavior of Iron Within Crevices in Nearly Neutral Chloride Solutions

Calculation of the Free Energy of Formation of Ferrous Chloride Tetrahydrate

Long term corrosion behavior of clad aluminum materials under different atmospheric conditions

Contact Info

Product

Resources

About