ISO/PWI 26589

Metallic and other inorganic coatings — Ferroin method for testing passive film integrity of stainless steels

Scope

This document provides recommendations and guidance for the inspection of passive film integrity on various stainless steels, including austenitic, martensitic, ferrite and duplex grades.
These procedures are intended to assist when it is necessary to ensure passive film integrity for a specific service condition. For example, insufficient development of the passive film during manufacturing or onsite installation may adversely affect the corrosion resistance of stainless steel components. Damage to the passive film may result in rust formation, raising concerns about product quality and competitiveness from the perspective of the purchaser.
This document provides recommendations for assessing three typical conditions related to passive film integrity during the manufacturing and installation of stainless steel components:
a) Passive film damage caused by contamination from iron sources, including but not limited to: iron tool marks, residual iron salts from pickling solutions, iron dust, atmospheric exposure, iron deposits in welds, embedded iron, iron oxides, or residual oxide scales remaining after grinding, machining, heat treatment, welding, or flame rectification. These contaminants are generally more sensitively detected by the ferroin method than by conventional ferroxyl testing.
b) Evaluation of passivation film quality following surface treatment processes such as cleaning, polishing, chemical passivation, electrochemical passivation, laser cleaning or laser passivation. Relevant defects include, but are not limited to: residual surface contaminants, post-treatment mechanical damage (e.g. scratches), or insufficient formation of a chromium-enriched oxide layer.
The selection of procedures to be applied to the parts shall be agreed upon between the supplier and the purchaser. For specific applications not covered by this document, additional requirements may be specified by agreement between the supplier and the purchaser.