Changes in friction of zinc flake coated threaded fasteners due to humidity, temperature and storage duration

The friction coefficient of a specific material combination is often assumed to be invariant in manufacturing processes such as during the tightening threaded fastener joints. This paper considers impact storage conditions on friction. Fasteners were stored hot humid and sub-zero temperature study thread under-head contacts. Four Zn-flake coatings, commonly used automotive industry considered. Consequent these fasteners at room revealed that history had significant their coefficients, halving some cases. varied behavior was considered response coating nano-hardness structure differences adsorption/absorption water zinc-oxide formation storage. • Fastener may jeopardize joint reliability. Water condensation leads more dramatic than adsorption. Storage lead drop by up 47%. Under-head affected