--- title: "Lean Amine Corrosion" slug: "lean-amine-corrosion-1" updated: 2026-10-27T23:12:43Z published: 2026-10-27T23:12:43Z canonical: "ims-handbook.cenosco.com/lean-amine-corrosion-1" --- > ## Documentation Index > Fetch the complete documentation index at: https://ims-handbook.cenosco.com/llms.txt > Use this file to discover all available pages before exploring further. # Lean Amine Corrosion ## Summary Lean Amine Corrosion is a general or localised form of corrosion, affecting primarily carbon and low-alloy steels. Pure (fresh) amine solutions are non-corrosive because of their alkalinity. The alkalinity of the amine solution (typically at a pH of 10.5-11.0) produces a passive iron oxide film on carbon steel. In addition, the lean amine solutions used in actual treating processes often contain small amounts of H2S and/or CO2. H2S reacts with steel to form an iron sulphide protective film. Small concentrations of CO2 in the absence of H2S can also form a somewhat protective iron carbonate film. When both CO2 and H2S are present, even relatively small concentrations of H2S tend to form sulphide films that provide the dominant protection. ### Detailed Guidance For detailed Guidance, see the attached PDF. A summary of the information, as it pertains to use in IMS is shown below. [PDF document](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/CEN.16.10656 - Lean Amine Corrosion.pdf?sv=2026-02-06&spr=https&st=2026-10-28T14%3A21%3A19Z&se=2026-10-28T15%3A21%3A19Z&sr=c&sp=r&sig=UWQ1JwcctG84aSMHuPGeWfuD4ef4cdeCnZWPQwXtR1E%3D)

Parameters affecting IOW – Step 2

See [Step 2](/v414/docs/step-2-identify-threats-and-barriers-define-the-cl-1). The following table is a generic IOW Table for Lean Amine Corrosion Loops. Generic IOW Table for Lean Amine Corrosion Loops: | Equipment/ Stream / Location (Tag) | Parameter | Measurement unit | Typical measurement frequency | Limit Category (and Type) | | --- | --- | --- | --- | --- | | Line from regenerator to lean amine pump; at regenerator outlet | Temperature | °C | TBD / Site specific | Standard / Monitoring (Max.) | | Outlet reboiler (liquid and gas (and liquid-gas) return lines. | Temperature | °C | TBD / Site specific | Standard / Monitoring (Max.) | | Lean solvent | Amine residual H2S loading (acid-gas loading) | ppmw | TBD / Site specific | Standard / Monitoring (Min.) | | Lean solvent | Amine residual CO2 loading (acid-gas loading) | ppmw | TBD / Site specific | Standard / Monitoring (Max.) | | All lean amine lines | Flow rate | m/s | Site specific (e.g., depends on stability of the operation) | Monitoring (Max.) | | Lean Amine | Solvent strength | wt.% | Typically, once a day (depends on frequency of fluctuations of the solvent strength) | Standard / Monitoring (Max.) | | Lean Amine | Chloride content | ppmw | TBD / Site specific | Monitoring (Max.) | | Lean Amine | pH | | TBD / Site specific / typically 3 times a week (but much more frequent than the "fingerprint" or "Huntsman" analyses). | Standard / Monitoring (Min.) | | Lean Amine | Temperature | °C | Continuously | Critical (Max.) | | Lean Amine | Maximal content of heat stable salts (HSS). | wt.% on total solvent | Site specific but recommended at least once per quarter and additional when the pH IOW is on or nearing the limit. | Monitoring (Max.) | | Lean Amine | Maximal Total Suspended Solids (TSS) | ppmw | TBD / Site specific | Monitoring (Max.) |

Confidence – Step 10

 See [Step 10](/v414/docs/step-10-assess-the-confidence-1): Follow the guidance below to determine answers for the Lean Amine Corrosion Confidence Assessment. Lean Amine Corrosion Confidence Assessment Guidance: | Key Questions | Guidance | | --- | --- | | Degradation mechanism can be properly controlled. | - "Yes": HSAS, minimum acid gas loading and the other IOWs in the table above are properly controlled; residual acid-gas loading under control and minimum value established. - "No": When one or more IOW limits are frequently exceeded. | | Relevant process parameters are reliably monitored. | - "Yes": All relevant process variables known and actively monitored. - "Intermediate": Relevant process variables known but not actively monitored; no limits for operations. - "No": No IOW available. | | Reliable inspections were carried out. | - "Yes": 3 inspections above ‘usually effective’. - "Intermediate": 1 – 2 inspections above ‘usually effective’. - "No": No inspections or ineffective inspections. |

Required Inspection Effectiveness – Step 11 & Step 12

 See [Step 11](/v414/docs/step-11-review-the-results-nid-mii-is-inspection-effectiveness) and [Step 12](/v414/docs/step-12-assign-s-rbi-results-to-inspectioncorrosion-schedules-andor-update-monitoring-plan). Use the Required Inspection Effectiveness, determined in [Step 11](/v414/docs/step-11-review-the-results-nid-mii-is-inspection-effectiveness), to determine the Inspection technique and coverage. In [Step 11](/v414/docs/methodology-step-11) you can find guidance for General Thinning. The below table provide guidance for Localized Thinning. Lean amine corrosion tends to be localized in nature.

The inspection technique and coverage, for Localized Thinning, to achieve a required Inspection Effectiveness:

 | Required Inspection Effectiveness | Intrusive Inspection | Non-Intrusive Inspection | | --- | --- | --- | | A (Highly) Effective | Visual examination of 90 -100% of susceptible areas (with removal of internal packing, trays, etc.) and thickness measurements. | 90-100% coverage using (automated) ultrasonic scanning or profile radiography of susceptible areas. Inspection of a smaller percentage area is acceptable if the corrosion mechanism is well understood, and susceptible areas known; lower coverage could still provide the level of confidence needed. | | B (Usually) Effective | Visual examination of at least 70% of susceptible areas (with partial removal of the internals) including manways, nozzles, etc. and thickness measurements at noted areas of concern. | Inspect 70% of susceptible areas using (automated) ultrasonic scanning, manual ultrasonic measurements (using surface scanning), or profile radiography. Inspection of a smaller percentage area is acceptable if the corrosion mechanism is well understood, and susceptible areas known; lower coverage could still provide the level of confidence needed. | | C (Fairly) Effective | Visual examination of at least 50% of suspect areas and spot ultrasonic thickness measurements at noted areas of concern. | Inspect 50% of susceptible areas1 using (automated) ultrasonic scanning, manual ultrasonic measurements (using suface scanning technique), or profile radiography. | | D (Poorly) Effective | Any visual examination of less than 50% of suspect area. | Spot ultrasonic thickness measurements or profile radiography without areas being specified by a corrosion engineer or other knowledgeable specialist, e.g., fixed number of CMS with fixed CML configuration without area scanning of individual measurement points (MPs). | | E Ineffective | N/A. | N/A. |