Corrosion & Scaling Monitor

The Corrosion & Scaling Monitor (CSM) evaluates corrosion and scaling risks in pipes, heat exchangers, and metallic equipment from an aqueous DWSIM material stream. It is a unit operation extension: it is attached to a Pipe Segment, a Heat Exchanger or an Advanced Shell-and-Tube Heat Exchanger through Tools \(\rightarrow\) Unit Operation Extension Manager, and it runs each time the host unit operation is calculated. It reads the host’s inlet stream and its calculated temperature, pressure and velocity profiles, and it leaves every stream unchanged. Results are written as extra properties of the host unit operation (keys starting with CSA_) and as a Markdown report in CSA_MarkdownReport, which opens in the Markdown Report Viewer.

The calculation is organised in four sequential modules: (1) ionic speciation; (2) corrosion rates; (3) scaling indices; (4) remaining useful life and inhibitor dosing.

Ionic Speciation

Ionic speciation determines the concentrations and activities of ions in solution from the analytical (total) composition of the stream (total carbon, sulfide, sulfate and metal cation concentrations) and the operating conditions \(T\) and \(P\).

Ionic Strength

The ionic strength \(I\) (mol kg\(^{-1}\)) is calculated as:

\[ I = \frac{1}{2}\sum_{i} m_i z_i^2 \]

where \(m_i\) is the molality of ion \(i\) (mol kg\(^{-1}\)) and \(z_i\) is its charge number.

Activity Coefficients

The Extended Debye–Hückel model (EDHE) is used with individual ionic size parameters \(a_i\) :

\[ \log_{10}\gamma_i = -\frac{A\,z_i^2\,\sqrt{I}}{1 + B\,a_i\,\sqrt{I}} \]

The Debye–Hückel parameters \(A\) and \(B\) vary with temperature according to the correlations of :

\[ \begin{align} A(T) &= 1.131 + 1.335\times10^{-3}(T-298.15) + 1.164\times10^{-5}(T-298.15)^2 \\ B(T) &= 3.281 + 5.793\times10^{-3}(T-298.15) \end{align} \]

where \(T\) is temperature in kelvin. For ionic strengths above 0.5 mol kg\(^{-1}\), the Davies model is used as an alternative:

\[ \log_{10}\gamma_i = -A\,z_i^2 \left(\frac{\sqrt{I}}{1+\sqrt{I}} - 0.3\,I\right) \]

Equilibrium Constants

All equilibrium constants are corrected for temperature. The water ionization constant follows :

\[ \ln K_w(T) = -\frac{4808.1}{T} - 7.077\ln T + 26.88 \]

For the carbonate system, the first and second dissociation constants of carbonic acid are:

\[ \begin{align} \log_{10}K_{a1,\mathrm{CO_{2}}}(T) &\approx -6.35 + 5.0\times10^{-3}(T-298.15) \\ \log_{10}K_{a2,\mathrm{CO_{2}}}(T) &\approx -10.33 - 1.4\times10^{-2}(T-298.15) \end{align} \]

and for the sulfide system :

\[ \log_{10}K_{a1,\mathrm{H_{2}S}}(T) \approx -6.99 - 6.0\times10^{-3}(T-298.15) \]

Solution Procedure

The electrical charge balance of the solution is:

\[ \sum_{\mathrm{cations}} z_i m_i = \sum_{\mathrm{anions}} |z_j| m_j \]

The pH is determined iteratively by Newton–Raphson until \(|\Delta\mathrm{pH}| < 10^{-8}\) and \(|\Delta I| < 10^{-6}\), recomputing activity coefficients at each iteration. The activity of each species is then:

\[ a_i = \gamma_i \, m_i \]

Table 58 lists the ionic size parameters \(a_i\) and charges \(z_i\) used in the EDHE model.

Ion	Formula	\(z_i\)	\(a_i\) (Å)
Hydrogen	H\(^{+}\)	1	9.0
Hydroxide	OH\(^{-}\)	-1	3.5
Calcium	Ca\(^{2+}\)	2	6.0
Magnesium	Mg\(^{2+}\)	2	8.0
Barium	Ba\(^{2+}\)	2	5.0
Strontium	Sr\(^{2+}\)	2	5.0
Iron(II)	Fe\(^{2+}\)	2	6.0
Iron(III)	Fe\(^{3+}\)	3	9.0
Sodium	Na\(^{+}\)	1	4.0
Potassium	K\(^{+}\)	1	3.0
Chloride	Cl\(^{-}\)	-1	3.0
Sulfate	SO\(_{4}^{2-}\)	-2	4.0
Bicarbonate	HCO\(_{3}^{-}\)	-1	4.0
Carbonate	CO\(_{3}^{2-}\)	-2	4.5
Bisulfide	HS\(^{-}\)	-1	3.5
Sulfide	S\(^{2-}\)	-2	5.0

Ionic parameters for the Extended Debye–Hückel model .

Corrosion Rate Models

Three corrosion mechanisms are evaluated independently. The total corrosion rate is conservatively estimated as the sum of individual contributions:

\[ \mathrm{CR}_{\mathrm{total}} = \mathrm{CR}_{\mathrm{CO_{2}}} + \mathrm{CR}_{\mathrm{O_{2}}} + \mathrm{CR}_{\mathrm{H_{2}S}} \]

Risk is classified according to the thresholds of NACE SP0775 (Table 59).

Classification	\(\mathrm{CR}_{\mathrm{total}}\) (mm/yr)
Negligible	\(<0.025\)
Low	\(0.025\)–\(0.1\)
Moderate	\(0.1\)–\(0.25\)
High	\(0.25\)–\(1.0\)
Severe	\(>1.0\)

Corrosion risk classification .

CO\(_{2}\) Corrosion: de Waard & Milliams Model

The CO\(_{2}\) corrosion rate is calculated using the de Waard & Milliams model , extensively validated for oil and gas systems:

\[ \log_{10}\mathrm{CR}_{\mathrm{base}} = 5.8 - \frac{1710}{T} + 0.67\,\log_{10}p_{\mathrm{CO_{2}}} \]

where \(T\) is temperature in kelvin and \(p_{\mathrm{CO_{2}}}\) is the CO\(_{2}\) partial pressure in bar. This is the equation behind the de Waard–Milliams nomogram. The result is in mm/yr for bare carbon steel at the reference condition (\(\mathrm{pH} \approx 3.8\), no protective film).

The corrected rate is:

\[ \mathrm{CR}_{\mathrm{CO_{2}}} = \mathrm{CR}_{\mathrm{base}}\; f_{T}\; f_{\mathrm{pH}}\; f_{m}\; f_{\mathrm{mat}} \]

Temperature factor \(f_{T}\): above approximately 60 °C a precipitated FeCO\(_{3}\) layer becomes protective, reducing the corrosion rate. Values are based on NORSOK M-506 (Table 60).

Temperature (°C)	\(f_{T}\)
\(<60\)	1.00
60–80	0.80
80–100	0.60
100–120	0.30
\(>120\)	0.15

Temperature factor \(f_{T}\) for CO\(_{2}\) corrosion .

pH factor \(f_{\mathrm{pH}}\): correction relative to the reference pH of a CO\(_{2}\)-only solution (no added alkalinity):

\[ f_{\mathrm{pH}} = \min\!\left(10,\; 10^{0.317\,(\mathrm{pH}_{\mathrm{ref}} - \mathrm{pH})}\right) \]

The upper limit of 10 prevents pH from reducing the rate by more than one order of magnitude below the reference.

Mass-transfer factor \(f_{m}\): the reaction at the steel surface and the transport of dissolved CO\(_{2}\) to the wall act as resistances in series :

\[ \begin{align} \frac{1}{\mathrm{CR}} &= \frac{1}{V_{r}} + \frac{1}{V_{m}} \\ V_{m} &= 2.45\,\frac{U^{0.8}}{d^{0.2}}\,p_{\mathrm{CO_{2}}} \\ f_{m} &= \frac{V_{m}}{V_{r} + V_{m}} \end{align} \]

where \(V_{r} = \mathrm{CR}_{\mathrm{base}}\,f_{\mathrm{pH}}\) is the reaction-controlled rate (mm/yr), \(V_{m}\) is the mass-transfer-limited rate (mm/yr), \(U\) is the liquid velocity (m s\(^{-1}\)), \(d\) is the internal diameter (m) and \(p_{\mathrm{CO_{2}}}\) is in bar. The factor approaches 1 when mass transfer is fast (\(V_{m} \gg V_{r}\)) and falls as the flow slows. When no velocity is available the factor is 1.

Material factor \(f_{\mathrm{mat}}\): corrosion-resistant alloys exhibit substantially lower rates than carbon steel (Table 61).

Material	\(f_{\mathrm{mat}}\)
Carbon steel (API 5L X52/X65)	1.000
13% Cr martensitic alloy steel	0.050
Duplex stainless steel 2205	0.010
Inconel 625	0.001
Titanium Gr. 2	0.000

Material factor \(f_{\mathrm{mat}}\) for CO\(_{2}\) corrosion.

Dissolved O\(_{2}\) Corrosion

Oxygen corrosion is controlled by the cathodic limiting current for O\(_{2}\) reduction:

\[ i_{L} = 4F\,k_{m,\mathrm{O_{2}}}\,[\mathrm{O_{2}}] \]

where \(F = 96485\) C mol\(^{-1}\), \(k_{m,\mathrm{O_{2}}}\) is the O\(_{2}\) mass-transfer coefficient (m s\(^{-1}\)), and \([\mathrm{O_{2}}]\) is the molar concentration (mol L\(^{-1}\)). Conversion to corrosion rate (NACE RP0176 factor for iron, \(n=2\)):

\[ \mathrm{CR}_{\mathrm{O_{2}}} = i_{L}\,f_{T}\,f_{\mathrm{Cl}}\,f_{\mathrm{mat}} \times 1.16\times10^{-3} \]

The chloride factor accounts for passive film breakdown:

\[ f_{\mathrm{Cl}} = 1 + 0.5\,\log_{10}\!\left(1 + \frac{m_{\mathrm{Cl^{-}}}}{0.1}\right) \]

H\(_{2}\)S Corrosion and SSC Assessment

The uniform H\(_{2}\)S corrosion rate follows :

\[ \mathrm{CR}_{\mathrm{H_{2}S}} = 0.1\,p_{\mathrm{H_{2}S}}^{0.36}\, \exp\!\left[-3200\!\left(\frac{1}{T}-\frac{1}{298.15}\right)\right] f_{v}\,f_{\mathrm{pH}}\,f_{\mathrm{mat}} \]

where \(p_{\mathrm{H_{2}S}}\) is in kPa and:

\[ f_{v} = 1 + 0.15\,v^{1.2} \]

with \(v\) the fluid velocity in m s\(^{-1}\).

Sulfide Stress Cracking (SSC) assessment follows NACE MR0175 / ISO 15156 . The severity index is:

\[ \begin{align} \mathrm{IS} &= \mathrm{pH}_{\mathrm{lim}} - \mathrm{pH} \\ \mathrm{pH}_{\mathrm{lim}} &= 3.5 + 0.5\,\log_{10}\!\left(\frac{p_{\mathrm{H_{2}S}}}{100}\right) \end{align} \]

SSC risk is flagged when IS \(>0\), \(p_{\mathrm{H_{2}S}} \geq 0.3\) kPa, hardness exceeds 250 HB (22 HRC) or working stress exceeds 450 MPa, and the material is susceptible (carbon steel or 13% Cr).

Scaling Indices

The general saturation index \(\mathrm{SI}_{i}\) for mineral species \(i\) is:

\[ \mathrm{SI}_{i} = \log_{10}\!\frac{Q_{i}}{K_{\mathrm{sp},i}(T)} \]

where \(Q_{i}\) is the ionic product computed from ionic activities and \(K_{\mathrm{sp},i}(T)\) is the solubility product. \(\mathrm{SI} > 0\) indicates supersaturation (precipitation risk); \(\mathrm{SI} < 0\) indicates undersaturation.

Solubility Products

Temperature-dependent \(K_{\mathrm{sp}}\) values are given in Table 62.

Mineral	Formula	\(\log_{10}K_{\mathrm{sp}}(T)\)
Calcite	CaCO\(_{3}\)	\(-171.91 - 0.0780\,T + 2839.3/T + 71.60\log_{10}T\)
Gypsum	CaSO\(_{4}{\cdot}2\)H\(_{2}\)O	\(-4.481 + 9.516\times10^{-3}T_{C} - 1.077\times10^{-4}T_{C}^{2}\)
Anhydrite	CaSO\(_{4}\)	\(-4.268 - 1.869\times10^{-3}T_{C} + 2.577\times10^{-7}T_{C}^{2}\)
Barite	BaSO\(_{4}\)	\(-9.90 - 1.24\times10^{-2}T_{C} + 5.9\times10^{-5}T_{C}^{2}\)
Celestite	SrSO\(_{4}\)	\(-6.63 - 6.7\times10^{-3}T_{C}\)
Siderite	FeCO\(_{3}\)	\(-10.89 + 3.0\times10^{-3}(T-298.15)\)
Mackinawite	FeS	\(-3.60 - 8.0\times10^{-3}(T-298.15)\)

Solubility product correlations for the main mineral phases.

\(T\) in kelvin; \(T_{C} = T - 273.15\) in °C.

Langelier Saturation Index (LSI)

The LSI quantifies the CaCO\(_{3}\) precipitation tendency:

\[ \mathrm{LSI} = \mathrm{pH} - \mathrm{pH}_{s} \]

\[ \mathrm{pH}_{s} = \log_{10}\!\frac{K_{a2}}{K_{\mathrm{sp,calcite}}} - \log_{10}(a_{\mathrm{Ca^{2+}}}) - \log_{10}(a_{\mathrm{HCO_{3}^{-}}}) \]

LSI \(> 0\): scale-forming; LSI \(< 0\): corrosive (undersaturated).

Ryznar Stability Index (RSI)

The RSI provides better field correlation than LSI:

\[ \mathrm{RSI} = 2\,\mathrm{pH}_{s} - \mathrm{pH} \]

Interpretation is given in Table 63.

RSI	Tendency
\(<4.5\)	Severe scaling
4.5–5.5	Heavy scaling
5.5–6.5	Some scaling
6.5–7.0	Stable / slight scaling tendency
7.0–8.0	Stable / slightly corrosive
8.0–9.0	Corrosive
\(>9.0\)	Highly corrosive

Interpretation of the Ryznar Stability Index .

Stiff–Davis Index (SDI)

For high-ionic-strength solutions (\(I > 0.5\) mol kg\(^{-1}\), e.g. seawater and produced brines), the SDI corrects for the salinity effect on calcite solubility:

\[ \mathrm{SDI} = \mathrm{pH} - (p\mathrm{Ca} + p\mathrm{Alk} + K') \]

\[ K'(T,I) = \bigl[1.845 + 8.0\times10^{-3}\,T_{C} - 1.0\times10^{-4}\,T_{C}^{2}\bigr] - 0.45\,\sqrt{I} - 0.06\,I \]

Remaining Useful Life

The Remaining Useful Life (RUL) analysis follows API570 and API 579-1 / ASME FFS-1 .

Retirement Thickness

The minimum required thickness per ASME B31.3 §304.1.2 is:

\[ t_{\mathrm{req}} = \frac{P\,D}{2(SE + PY)} \]

where \(P\) is design pressure (MPa), \(D\) outside diameter (mm), \(S\) allowable stress (MPa), \(E\) weld joint efficiency, and \(Y = 0.4\) for carbon/alloy steel below 482 °C. The retirement thickness is \(t_{\mathrm{ret}} = \max(t_{\min}, t_{\mathrm{req}})\).

Design Corrosion Rate

The design rate is the more conservative of the mechanistic model and the inspection-derived rate:

\[ \mathrm{CR}_{\mathrm{design}} = \max(\mathrm{CR}_{\mathrm{model}},\;\mathrm{CR}_{\mathrm{measured}}) \]

\[ \mathrm{CR}_{\mathrm{measured}} = \frac{t_{\mathrm{prev}} - t_{\mathrm{last}}} {\Delta t_{\mathrm{insp}}} \]

RUL Calculation (API 570 Eq. 6.1)

The estimated current thickness is:

\[ t_{\mathrm{current}} = t_{\mathrm{last}} - \mathrm{CR}_{\mathrm{design}}\,\Delta t \]

and the remaining useful life:

\[ \mathrm{RUL} = \frac{t_{\mathrm{current}} - t_{\mathrm{ret}}} {\mathrm{CR}_{\mathrm{design}}} \]

The projected life is capped at 100 years, since a corrosion rate close to zero gives an unbounded value.

Component Basis in the Extension Run

When the monitor runs as an extension, the remaining life is evaluated where the corrosion rate is highest: the pipe section with the highest rate, or the exchanger segment with the highest rate. The wall is taken as new at its nominal thickness, since the flowsheet carries no inspection history, and the design pressure is the inlet pressure of the pipe or of the exchanger’s process side. For a pipe, \(t_{\min}\) is a structural minimum by pipe size (1.8 mm up to NPS 2, 2.0 mm for NPS 3, 2.3 mm for NPS 4, 2.8 mm for NPS 6 to 18 and 3.1 mm above), limited to half the nominal wall. For an exchanger tube, \(t_{\min}\) is 60 % of the nominal wall, which corresponds to the usual plugging criterion of 40 % wall loss. When the exchanger has no shell-and-tube geometry, a 19.05 mm \(\times\) 2.11 mm tube is assumed.

MAWP and Inspection Interval

The Maximum Allowable Working Pressure at the current thickness (ASME B31.3) is:

\[ \mathrm{MAWP} = \frac{2\,S\,E\,t_{\mathrm{current}}}{D - 2\,Y\,t_{\mathrm{current}}} \]

If \(\mathrm{MAWP} < P_{\mathrm{design}}\), a de-rating alert is generated.

The inspection interval is set to the lesser of the risk-category maximum and half the RUL :

\[ t_{\mathrm{insp}} = \min\!\bigl(t_{\mathrm{max,cat}},\;\tfrac{1}{2}\,\mathrm{RUL}\bigr) \]

Corrosion risk	\(t_{\mathrm{max,cat}}\) (years)
Negligible	15
Low	10
Moderate	5
High	2
Severe	1

Maximum inspection intervals by risk category .

Chemical Inhibitor Dosing

In the extension run, the corrosion inhibitor is sized at the point with the highest corrosion rate and the scale inhibitors at the point with the highest LSI. The injection volumes use the liquid volumetric flow of the host’s inlet stream, with the default targets of Table 66.

Corrosion Inhibitor

The inhibition efficiency of film-forming amines and phosphates follows the Langmuir adsorption model :

\[ \eta = 100\,\bigl[1 - e^{-k_{\mathrm{ads}}\,C_{\mathrm{inh}}}\bigr] \]

\[ k_{\mathrm{ads}}(T) = k_{\mathrm{ads}}^{0}\, \exp\!\left[-E_{a}\!\left(\frac{1}{T}-\frac{1}{298.15}\right)\right] \]

Parameters by inhibitor family are listed in Table 65.

Type	Application	\(k_{\mathrm{ads}}^{0}\) (L mg\(^{-1}\))	\(E_{a}\) (K)
Imidazoline + amide	CO\(_{2}\)	0.060	1200
Quaternary imidazoline	CO\(_{2}\)/H\(_{2}\)S	0.055	1500
Zinc salt + phosphate	O\(_{2}\)	0.040	—
Zinc phosphate film-former	General	0.050	—

Adsorption parameters for the main corrosion inhibitor families .

The required dose and daily product volume are:

\[ C_{\mathrm{inh}} = -\frac{1}{k_{\mathrm{ads}}}\, \ln(1 - \eta^{*}), \qquad \eta^{*} = 1 - \frac{\mathrm{CR}^{*}}{\mathrm{CR}_{\mathrm{total}}} \]

\[ V_{\mathrm{prod}} = \frac{C_{\mathrm{inh}}\,Q}{1000\,\chi_{\mathrm{active}}} \]

where \(Q\) is the fluid flow rate (m\(^{3}\) day\(^{-1}\)) and \(\chi_{\mathrm{active}}\) is the mass fraction of active ingredient in the commercial product.

Scale Inhibitors: Threshold Model

Threshold inhibition relies on sub-stoichiometric phosphonate or polymer concentrations to block crystal growth . The threshold dose for CaCO\(_{3}\) is:

\[ C_{\mathrm{th,CaCO_{3}}} = A\, \sqrt{\frac{c_{\mathrm{Ca^{2+}}}}{1000} \cdot \frac{c_{\mathrm{HCO_{3}^{-}}}}{1000}}\; (\mathrm{LSI})^{0.6}\; e^{0.02(T_{C} - 25)}\; (1 + 0.3\sqrt{I}) \]

where \(c\) is in mg L\(^{-1}\) and \(A = 0.8\) for HEDP (LSI \(< 1.5\)) or \(A = 1.8\) for DTPMP (LSI \(\geq 1.5\)).

For BaSO\(_{4}\) :

\[ C_{\mathrm{th,BaSO_{4}}} = 0.45\, \sqrt{c_{\mathrm{Ba^{2+}}}}\; \mathrm{SI}_{\mathrm{Barite}}^{0.7}\; e^{0.025(T_{C} - 25)}\; (1 + 0.5\sqrt{I}) \]

When \(\mathrm{SI}_{\mathrm{Barite}} > 2.0\), threshold inhibition alone may be insufficient; sulfate removal by nanofiltration or produced-water dilution should be evaluated.

For CaSO\(_{4}\) (gypsum / anhydrite), ATMP and polyacrylate blends are preferred:

\[ C_{\mathrm{th,CaSO_{4}}} = 1.5\, \sqrt{\frac{c_{\mathrm{Ca^{2+}}}}{1000} \cdot \frac{c_{\mathrm{SO_{4}^{2-}}}}{1000}}\; (\mathrm{SI}_{\mathrm{max}} + 1)^{0.7}\; e^{0.015(T_{C} - 25)} \]

The estimated daily chemical cost is:

\[ C_{\mathrm{chem}} = c_{\mathrm{unit}}\, \sum_{j} V_{\mathrm{prod},j} \]

where \(c_{\mathrm{unit}}\) is the unit product cost (USD L\(^{-1}\); default: 3.50 USD L\(^{-1}\)).

Incremental Analysis in Heat Exchangers

The temperature gradient along a heat exchanger alters local equilibrium constants, saturation indices, and corrosion rates. The CSM divides the exchanger into \(N\) segments (\(N = 20\) by default) with linear interpolation:

\[ \begin{align} T_{\mathrm{fluid},i} &= T_{\mathrm{in}} + \frac{i}{N-1}\,(T_{\mathrm{out}} - T_{\mathrm{in}}) \\ T_{\mathrm{wall},i} &= T_{w,\mathrm{in}} + \frac{i}{N-1}\,(T_{w,\mathrm{out}} - T_{w,\mathrm{in}}) \end{align} \]

In each segment \(i\), speciation is recomputed at the local temperature while keeping the inlet analytical concentrations (no accumulated precipitation), and all corrosion and scaling modules are evaluated at the local wall temperature \(T_{\mathrm{wall},i}\).

The precipitation front is defined as the relative axial position \(x_{f}\) where the LSI crosses zero, indicating the onset of CaCO\(_{3}\) deposition along the tube bundle.

Configuration Parameters

All configurable parameters and their defaults are listed in Table 66. When the monitor runs as an extension, the geometry, velocity, pressure and flow come from the host unit operation (Sections 10.4 and 10.5) and the other entries keep their defaults.

Configuration parameters of the Corrosion & Scaling Monitor.

Parameter	Unit	Default	Description
Table 66 (continued)
Parameter	Unit	Default	Description
Continued on next page…
Internal diameter	m	0.1016	Internal pipe diameter
Fluid velocity	m s\(^{-1}\)	1.0	Mean flow velocity
\(p_{\mathrm{CO_{2}}}\)	bar	0	CO\(_{2}\) partial pressure (0 = compute)
\(p_{\mathrm{H_{2}S}}\)	kPa	0	H\(_{2}\)S partial pressure (0 = compute)
Dissolved O\(_{2}\)	ppb	0	Dissolved oxygen
Material	—	C. steel	Material grade
Working stress	MPa	200	Operating stress
Hardness	HB	200	Brinell hardness
Nominal thickness	mm	9.53	Nominal wall thickness
Minimum thickness	mm	3.0	Minimum allowable thickness
Outside diameter	mm	114.3	Outside diameter
Design pressure	MPa	5.0	Design pressure
Allowable stress	MPa	138.0	Material allowable stress
Last meas. thickness	mm	0	Last UT inspection thickness
Last measurement date	—	—	Date of last UT inspection
Previous thickness	mm	0	Previous inspection thickness
Previous meas. date	—	—	Date of previous inspection
Installation date	—	—	Component installation date
Fluid flow rate	m\(^{3}\) day\(^{-1}\)	100	Total volumetric flow rate
Target corr. rate	mm/yr	0.10	Corrosion rate target after inhibition
Target LSI	—	0.0	Langelier index target
Chemical cost	USD L\(^{-1}\)	3.50	Unit cost of chemical product

Output Properties

After calculation, results are available as ExtraProperties of the host unit operation, accessible through the DWSIM object editor, the IronPython console, and the CAPE-OPEN API (Table 67). A pipe segment also carries per-section keys (CSA_Sec{n}_…) and per-increment profiles (CSA_Inc…); a heat exchanger carries the conditions of its worst corrosion and scaling segments (CSA_WorstCR_…, CSA_WorstLSI_…).

Property	Unit	Description
CSA_MaxCR_mmyr	mm/yr	Highest total corrosion rate
CSA_MaxLSI	—	Highest Langelier Saturation Index
CSA_MaxSI_Barite	—	Highest barite saturation index
CSA_MaxSI_Gypsum	—	Highest gypsum saturation index
CSA_HasSSCRisk	—	1 = SSC risk; 0 = no risk
CSA_RUL_yr	yr	Remaining useful life
CSA_CurrentThickness_mm	mm	Estimated current thickness
CSA_RetirementThickness_mm	mm	Retirement thickness
CSA_MAWP_MPa	MPa	MAWP at current thickness
CSA_IntegrityStatus	—	Integrity status (API 570)
CSA_NextInspection	—	Next inspection date
CSA_CorrInhib_Dose_ppm	ppm	Corrosion inhibitor dose
CSA_ChemCost_USD_day	USD/day	Daily chemical cost
CSA_TreatmentStrategy	—	Primary treatment strategy
CSA_MarkdownReport	—	Full report (Markdown)

Main output properties of the Corrosion & Scaling Monitor.