D2803-09 – Standard Test Method Technical Guide

📋 Scope and Mechanism of Filiform Corrosion

ASTM D2803-09 (Reapproved 2020) provides a standardized guide for evaluating the susceptibility of organic-coated metal substrates to filiform corrosion. Per the standard’s terminology, filiform corrosion is defined as a special type of under-film corrosion characterized by a definite threadlike structure and directional growth. This phenomenon usually occurs between 20 and 35 °C (70 to 95 °F), with a corresponding relative humidity (RH) range of 60 to 95 %. The standard specifically notes that above 95 % RH, blistering rather than filiform corrosion may occur, necessitating strict environmental control during testing. The guide is strictly limited to the determination of whether filiform corrosion will occur between the organic coating and the substrate.

🔬 Standard Test Procedures and Specimen Preparation

This guide covers three distinct procedures for initiating and propagating filiform corrosion. All procedures require the preparation