diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/Make/files b/src/phaseSystemModels/multiphaseInter/phasesSystem/Make/files
index ce9bf08878..37df8ee1b4 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/Make/files
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/Make/files
@@ -25,4 +25,6 @@ $(surfaceTension)/surfaceTensionModel/surfaceTensionModel.C
 $(surfaceTension)/constantSurfaceTensionCoefficient/constantSurfaceTensionCoefficient.C
 */
 
+derivedFvPatchFields/timeVaryingMassSorption/timeVaryingMassSorptionFvPatchScalarField.C
+
 LIB = $(FOAM_LIBBIN)/libincompressibleMultiphaseSystems
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/derivedFvPatchFields/timeVaryingMassSorption/timeVaryingMassSorptionFvPatchScalarField.C b/src/phaseSystemModels/multiphaseInter/phasesSystem/derivedFvPatchFields/timeVaryingMassSorption/timeVaryingMassSorptionFvPatchScalarField.C
new file mode 100644
index 0000000000..a57d9ebf09
--- /dev/null
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/derivedFvPatchFields/timeVaryingMassSorption/timeVaryingMassSorptionFvPatchScalarField.C
@@ -0,0 +1,282 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2021 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "timeVaryingMassSorptionFvPatchScalarField.H"
+#include "addToRunTimeSelectionTable.H"
+#include "fvPatchFieldMapper.H"
+#include "volFields.H"
+#include "EulerDdtScheme.H"
+#include "CrankNicolsonDdtScheme.H"
+#include "backwardDdtScheme.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+const Foam::Enum
+<
+    Foam::timeVaryingMassSorptionFvPatchScalarField::ddtSchemeType
+>
+Foam::timeVaryingMassSorptionFvPatchScalarField::ddtSchemeTypeNames_
+({
+    {
+        ddtSchemeType::tsEuler,
+        fv::EulerDdtScheme<scalar>::typeName_()
+    },
+    {
+        ddtSchemeType::tsCrankNicolson,
+        fv::CrankNicolsonDdtScheme<scalar>::typeName_()
+    },
+    {
+        ddtSchemeType::tsBackward,
+        fv::backwardDdtScheme<scalar>::typeName_()
+    },
+});
+
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::timeVaryingMassSorptionFvPatchScalarField::
+timeVaryingMassSorptionFvPatchScalarField
+(
+    const fvPatch& p,
+    const DimensionedField<scalar, volMesh>& iF
+)
+:
+    fixedValueFvPatchScalarField(p, iF),
+    kabs_(scalar(1)),
+    max_(scalar(1)),
+    kdes_(scalar(1))
+{}
+
+
+Foam::timeVaryingMassSorptionFvPatchScalarField::
+timeVaryingMassSorptionFvPatchScalarField
+(
+    const fvPatch& p,
+    const DimensionedField<scalar, volMesh>& iF,
+    const dictionary& dict
+)
+:
+    fixedValueFvPatchScalarField(p, iF, dict, false),
+    kabs_(dict.getCheck<scalar>("kabs", scalarMinMax::ge(0))),
+    max_(dict.getCheck<scalar>("max", scalarMinMax::ge(0))),
+    kdes_(dict.getCheckOrDefault<scalar>("kdes", 0, scalarMinMax::ge(0)))
+{
+    if (dict.found("value"))
+    {
+        fvPatchScalarField::operator=
+        (
+            scalarField("value", dict, p.size())
+        );
+    }
+    else
+    {
+        fvPatchField<scalar>::operator=(Zero);
+    }
+}
+
+
+Foam::timeVaryingMassSorptionFvPatchScalarField::
+timeVaryingMassSorptionFvPatchScalarField
+(
+    const timeVaryingMassSorptionFvPatchScalarField& ptf,
+    const fvPatch& p,
+    const DimensionedField<scalar, volMesh>& iF,
+    const fvPatchFieldMapper& mapper
+)
+:
+    fixedValueFvPatchScalarField(ptf, p, iF, mapper),
+    kabs_(ptf.kabs_),
+    max_(ptf.max_),
+    kdes_(ptf.kdes_)
+{}
+
+
+Foam::timeVaryingMassSorptionFvPatchScalarField::
+timeVaryingMassSorptionFvPatchScalarField
+(
+    const timeVaryingMassSorptionFvPatchScalarField& ptf
+)
+:
+    fixedValueFvPatchScalarField(ptf),
+    kabs_(ptf.kabs_),
+    max_(ptf.max_),
+    kdes_(ptf.kdes_)
+{}
+
+
+Foam::timeVaryingMassSorptionFvPatchScalarField::
+timeVaryingMassSorptionFvPatchScalarField
+(
+    const timeVaryingMassSorptionFvPatchScalarField& ptf,
+    const DimensionedField<scalar, volMesh>& iF
+)
+:
+    fixedValueFvPatchScalarField(ptf, iF),
+    kabs_(ptf.kabs_),
+    max_(ptf.max_),
+    kdes_(ptf.kdes_)
+{}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+void Foam::timeVaryingMassSorptionFvPatchScalarField::autoMap
+(
+    const fvPatchFieldMapper& m
+)
+{
+    fixedValueFvPatchScalarField::autoMap(m);
+}
+
+
+void Foam::timeVaryingMassSorptionFvPatchScalarField::rmap
+(
+    const fvPatchScalarField& ptf,
+    const labelList& addr
+)
+{
+    fixedValueFvPatchScalarField::rmap(ptf, addr);
+}
+
+
+Foam::tmp<Foam::scalarField>
+Foam::timeVaryingMassSorptionFvPatchScalarField::source() const
+{
+    auto tsource = tmp<scalarField>::New(patch().size(), Zero);
+    auto& source = tsource.ref();
+
+    const scalarField cp(*this);
+    const scalarField w(max(1 - cp/max_, scalar(0)));
+
+    source = -kabs_*w*max(patchInternalField() - cp, scalar(0));
+
+    source += kdes_*max(cp - patchInternalField(), scalar(0));
+
+    return tsource;
+}
+
+
+void Foam::timeVaryingMassSorptionFvPatchScalarField::updateCoeffs()
+{
+    if (updated())
+    {
+        return;
+    }
+
+    const label patchi = patch().index();
+
+    const scalar dt = db().time().deltaTValue();
+
+    const auto& fld =
+        db().lookupObject<volScalarField>(this->internalField().name());
+    const volScalarField& fld0 = fld.oldTime();
+
+    // Lookup d/dt scheme from database
+    const word ddtSchemeName(fld.mesh().ddtScheme(fld.name()));
+    const ddtSchemeType& ddtScheme = ddtSchemeTypeNames_[ddtSchemeName];
+
+    const scalarField cp(*this);
+    const scalarField w(max(1 - cp/max_, scalar(0)));
+
+    tmp<scalarField> dfldp =
+         kabs_
+        *w
+        *max(patchInternalField() - cp, scalar(0))
+        *dt;
+
+    dfldp.ref() -=
+        kdes_
+       *max(cp - patchInternalField(), scalar(0))
+       *dt;
+
+    switch (ddtScheme)
+    {
+        case tsEuler:
+        case tsCrankNicolson:
+        {
+            operator==(fld0.boundaryField()[patchi] + dfldp);
+
+            break;
+        }
+        case tsBackward:
+        {
+            const scalar dt0 = db().time().deltaT0Value();
+
+            const scalar c = scalar(1) + dt/(dt + dt0);
+            const scalar c00 = dt*dt/(dt0*(dt + dt0));
+            const scalar c0 = c + c00;
+
+            operator==
+                (
+                    (
+                        c0*fld0.boundaryField()[patchi]
+                     - c00*fld0.oldTime().boundaryField()[patchi]
+                     + dfldp
+                    )/c
+                );
+
+            break;
+        }
+        default:
+        {
+            FatalErrorInFunction
+                << ddtSchemeName << nl
+                << "    on patch " << this->patch().name()
+                << " of field " << this->internalField().name()
+                << " in file " << this->internalField().objectPath()
+                << exit(FatalError);
+        }
+    }
+
+    fixedValueFvPatchScalarField::updateCoeffs();
+}
+
+
+void Foam::timeVaryingMassSorptionFvPatchScalarField::write(Ostream& os) const
+{
+    fvPatchScalarField::write(os);
+
+    os.writeEntry("kabs", kabs_);
+    os.writeEntry("max", max_);
+    os.writeEntryIfDifferent<scalar>("kdes", scalar(0), kdes_);
+
+    writeEntry("value", os);
+}
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+    makePatchTypeField
+    (
+        fvPatchScalarField,
+        timeVaryingMassSorptionFvPatchScalarField
+    );
+}
+
+// ************************************************************************* //
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/derivedFvPatchFields/timeVaryingMassSorption/timeVaryingMassSorptionFvPatchScalarField.H b/src/phaseSystemModels/multiphaseInter/phasesSystem/derivedFvPatchFields/timeVaryingMassSorption/timeVaryingMassSorptionFvPatchScalarField.H
new file mode 100644
index 0000000000..0a8a3d753e
--- /dev/null
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/derivedFvPatchFields/timeVaryingMassSorption/timeVaryingMassSorptionFvPatchScalarField.H
@@ -0,0 +1,249 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2021 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    Foam::timeVaryingMassSorptionFvPatchScalarField
+
+Group
+    grpGenericBoundaryConditions
+
+Description
+    This boundary condition provides a first order fixed-value condition
+    for a given scalar field to model time-dependent adsorption-desoprtion
+    processes to be used with the \c interfaceOxideRate mass model
+
+    \f[
+        \frac{d c}{d t} =
+            k_{abs} w (c_{int} - c_{p_{w}}) + k_{des} (c_{p_{w} - c_{int}})
+    \f]
+
+    \f[
+        w = max(1 - c_{p_{w}/max, 0);
+    \f]
+
+    where
+    \vartable
+      c_{int}      | Concentration at cell
+      c_{p_{w}}    | Concentration at wall
+      k_{abs}      | Adsorption rate constant [1/s]
+      k_{des}      | Desorption rate constant [1/s]
+      w            | Weight function
+      max          | Max concentration at wall
+    \endvartable
+
+Usage
+    Example of the boundary condition specification:
+    \verbatim
+    <patchName>
+    {
+        // Mandatory entries
+        type        timeVaryingMassSorption;
+        kbas        <scalar>;
+        max         <scalar>;
+
+        // Optional entries
+        kdes        <scalar>;
+
+        // Inherited entries
+        ...
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property | Description                      | Type   | Reqd   | Deflt
+      type     | Type name: timeVaryingAdsorption | word   | yes    | -
+      kbas     | Adsorption rate constant         | scalar | yes    | -
+      max      | Maximum concentation at wall     | scalar | yes    | -
+      kdes     | Desorption rate constant         | scalar | no     | 0
+    \endtable
+
+    The inherited entries are elaborated in:
+      - \link fixedValueFvPatchFields.H \endlink
+
+SourceFiles
+    timeVaryingMassSorptionFvPatchScalarField.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef timeVaryingMassSorptionFvPatchScalarField_H
+#define timeVaryingMassSorptionFvPatchScalarField_H
+
+#include "fixedValueFvPatchFields.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+
+/*---------------------------------------------------------------------------*\
+             Class timeVaryingMassSorptionFvPatchScalarField Declaration
+\*---------------------------------------------------------------------------*/
+
+class timeVaryingMassSorptionFvPatchScalarField
+:
+    public fixedValueFvPatchScalarField
+{
+public:
+
+    // Public Enumeration
+
+        //- Enumeration defining the available ddt schemes
+        enum ddtSchemeType
+        {
+            tsEuler,
+            tsCrankNicolson,
+            tsBackward
+        };
+
+
+private:
+
+    // Private Data
+
+        //- Time scheme type names
+        static const Enum<ddtSchemeType> ddtSchemeTypeNames_;
+
+        //- Adsorption rate constant
+        scalar kabs_;
+
+        //- Maximum level of adsorption of a given substance on patch
+        scalar max_;
+
+        //- Desorption rate constant
+        scalar kdes_;
+
+
+public:
+
+    //- Runtime type information
+    TypeName("timeVaryingMassSorption");
+
+
+    // Constructors
+
+        //- Construct from patch and internal field
+        timeVaryingMassSorptionFvPatchScalarField
+        (
+            const fvPatch&,
+            const DimensionedField<scalar, volMesh>&
+        );
+
+        //- Construct from patch, internal field and dictionary
+        timeVaryingMassSorptionFvPatchScalarField
+        (
+            const fvPatch&,
+            const DimensionedField<scalar, volMesh>&,
+            const dictionary&
+        );
+
+        //- Construct by mapping given
+        //- timeVaryingMassSorptionFvPatchScalarField onto a new patch
+        timeVaryingMassSorptionFvPatchScalarField
+        (
+            const timeVaryingMassSorptionFvPatchScalarField&,
+            const fvPatch&,
+            const DimensionedField<scalar, volMesh>&,
+            const fvPatchFieldMapper&
+        );
+
+        //- Construct as copy
+        timeVaryingMassSorptionFvPatchScalarField
+        (
+            const timeVaryingMassSorptionFvPatchScalarField&
+        );
+
+        //- Construct and return a clone
+        virtual tmp<fvPatchScalarField> clone() const
+        {
+            return tmp<fvPatchScalarField>
+            (
+                new timeVaryingMassSorptionFvPatchScalarField(*this)
+            );
+        }
+
+        //- Construct as copy setting internal field reference
+        timeVaryingMassSorptionFvPatchScalarField
+        (
+            const timeVaryingMassSorptionFvPatchScalarField&,
+            const DimensionedField<scalar, volMesh>&
+        );
+
+        //- Construct and return a clone setting internal field reference
+        virtual tmp<fvPatchScalarField> clone
+        (
+            const DimensionedField<scalar, volMesh>& iF
+        ) const
+        {
+            return tmp<fvPatchScalarField>
+            (
+                new timeVaryingMassSorptionFvPatchScalarField(*this, iF)
+            );
+        }
+
+
+    // Member Functions
+
+        // Mapping
+
+            //- Map (and resize as needed) from self given a mapping object
+            virtual void autoMap
+            (
+                const fvPatchFieldMapper&
+            );
+
+            //- Reverse map the given fvPatchField onto this fvPatchField
+            virtual void rmap
+            (
+                const fvPatchScalarField&,
+                const labelList&
+            );
+
+        // Help
+
+            //- Return source rate
+            tmp<scalarField> source() const;
+
+
+        // Evaluation
+
+            //- Update the coefficients associated with the patch field
+            virtual void updateCoeffs();
+
+
+        //- Write
+        virtual void write(Ostream&) const;
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //