---
title: "PL External Corosion Theory"
slug: "pl-external-corosion-theory"
updated: 2026-10-27T23:12:11Z
published: 2026-10-27T23:12:11Z
canonical: "ims-handbook.cenosco.com/pl-external-corosion-theory"
---

> ## 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.

# PL External Corosion Theory

> [!NOTE]
> Take Note
> 
> This article introduces the theoretical underpinnings of External Corrosion as modelled in IMS PLSS. For guidance on entering data and interpreting results in the software, start with [PL External Corrosion Assessment](/v414/docs/plss-external-corrosion-assessment-1).

External corrosion is the deterioration of pipeline metal surfaces resulting from electrochemical reactions with the surrounding environment. For buried pipelines, the primary environment is soil or water. Left unmitigated, external corrosion reduces wall thickness over time, compromising structural integrity and ultimately leading to leaks, ruptures, or structural failures.

Effective management of external corrosion requires understanding the factors that control the corrosion rate, quantifying the combined effectiveness of protective barriers, and applying a predictive model to forecast future degradation. IMS PLSS implements the EXCOR corrosion prediction model for this purpose.

External corrosion is an Age-Related (AR) Degradation Mechanism. It is modelled using a Corrosion Rate (CR) and Remnant Life (RL). The assessment integrates data from multiple sources: soil surveys, coating inspections, Cathodic Protection (CP) surveys, and Inline Inspection (ILI) runs.