of either or bothofthesepartial reactions (anodic oxidation and/orcathodic
reduction). As ac onsequence, there can be anodic, cathodic,a nd mixed
inhibitors. Othert entative classification of inhibitors have been made by
takingi ntoc onsideration the chemical nature( organico ri norganic
substances), their characteristics (oxidizing or nonoxidizing compounds),
or their technological field of application(pickling, descaling, acid cleaning,
cooling water systems, etc.).
Inhibitors can be used in electrolytes at differentp Hv alues, from acid to
near-neutral or alkaline solutions. Because of the very different situations
created by changing various factors sucha sm edium and inhibitor in the
system metal/aggressive medium/inhibitor,various inhibition mechanisms
mustbec onsidered.
1–6
An accurate analysis of the different modes of inhibiting electrode
reactions including corrosion was carried out by Fischer.
7
He distinguished
among various mechanisms of action such as:
Interfacei nhibition
Electrolyte layer inhibition
Membrane inhibition
Passivation
Subsequently,Lorenz and Mansfield
8
proposed aclear distinctionbetween
interface and interphase inhibition, representing two different types of
retardation mechanisms of electrode reactions including corrosion. Interface
inhibition presumes as trong interaction between the inhibitor and the
corroding surface of the metal.
1,7,9
In this case,t he inhibitor adsorbs as a
potential-dependent, two-dimensional layer.T his layer can affect the basic
corrosion reactions in different ways:
By ag eometric blocking effect of the electrode surfaceb ecause of
the adsorption of as table inhibitor at ar elatively high degree
of coverage of the metal surface
By ab lockinge ffect of the surfaces ites because of the adsorption of
as tablei nhibitor at ar elatively low degree of coverage
By areactive coverage of the metal surface. In this case,the adsorption
process is followed by electrochemical or chemical reactions of the
inhibitor at the interface
Accordingt oL orenze and Mansfield,
8
interface inhibitiono ccurs in
corroding systems exhibiting ab are metal surface in contact with the
corrosivem edium. This conditioni so ftenr ealizedf or active metal
dissolution in acid solutions.
Interphase inhibition presumes at hree-dimensional layer between the
corroding substrate and the electrolyte.
7,10,11
Such layers generally consist of
weakly soluble corrosion products and/ori nhibitors. Interphase inhibition
Corrosion of Linings and Coatings
56
CAT8247—CHAPTER 3—6/10/2006—19:23—KADAMBADI—XMLMODEL B–p p. 55–68
reduction). As ac onsequence, there can be anodic, cathodic,a nd mixed
inhibitors. Othert entative classification of inhibitors have been made by
takingi ntoc onsideration the chemical nature( organico ri norganic
substances), their characteristics (oxidizing or nonoxidizing compounds),
or their technological field of application(pickling, descaling, acid cleaning,
cooling water systems, etc.).
Inhibitors can be used in electrolytes at differentp Hv alues, from acid to
near-neutral or alkaline solutions. Because of the very different situations
created by changing various factors sucha sm edium and inhibitor in the
system metal/aggressive medium/inhibitor,various inhibition mechanisms
mustbec onsidered.
1–6
An accurate analysis of the different modes of inhibiting electrode
reactions including corrosion was carried out by Fischer.
7
He distinguished
among various mechanisms of action such as:
Interfacei nhibition
Electrolyte layer inhibition
Membrane inhibition
Passivation
Subsequently,Lorenz and Mansfield
8
proposed aclear distinctionbetween
interface and interphase inhibition, representing two different types of
retardation mechanisms of electrode reactions including corrosion. Interface
inhibition presumes as trong interaction between the inhibitor and the
corroding surface of the metal.
1,7,9
In this case,t he inhibitor adsorbs as a
potential-dependent, two-dimensional layer.T his layer can affect the basic
corrosion reactions in different ways:
By ag eometric blocking effect of the electrode surfaceb ecause of
the adsorption of as table inhibitor at ar elatively high degree
of coverage of the metal surface
By ab lockinge ffect of the surfaces ites because of the adsorption of
as tablei nhibitor at ar elatively low degree of coverage
By areactive coverage of the metal surface. In this case,the adsorption
process is followed by electrochemical or chemical reactions of the
inhibitor at the interface
Accordingt oL orenze and Mansfield,
8
interface inhibitiono ccurs in
corroding systems exhibiting ab are metal surface in contact with the
corrosivem edium. This conditioni so ftenr ealizedf or active metal
dissolution in acid solutions.
Interphase inhibition presumes at hree-dimensional layer between the
corroding substrate and the electrolyte.
7,10,11
Such layers generally consist of
weakly soluble corrosion products and/ori nhibitors. Interphase inhibition
Corrosion of Linings and Coatings
56
CAT8247—CHAPTER 3—6/10/2006—19:23—KADAMBADI—XMLMODEL B–p p. 55–68