ISO 18953:2025

Steel structures — Structural bolting — Test methods to determine loss of pretension from faying surface coatings ISO 18953:2025

Publication date:   Dec 12, 2025

Scope

This document specifies test methods to determine loss of pretension in high-strength bolts due to the presence of coatings on the faying surface(s) of a bolted joint to be used in structural steelwork, when any of the coatings are thick enough to affect the pretension in a bolt in the short term, or can show significant deformation over time under sustained loads (creep-prone materials).
The presence within the grip of the bolt of other materials having considerably smaller stiffness than steel, such as insulation, is not included in this test method.