ISO 14713-3:2017

Overview

ISO 14713-3:2017 - "Zinc coatings - Guidelines and recommendations for the protection against corrosion of iron and steel in structures - Part 3: Sherardizing" provides practical guidance on designing and preparing ferrous articles for sherardizing (thermal diffusion zinc coating). The standard explains process limits, recommended surface preparation, design considerations, typical coating thicknesses and post-treatment practice. It clarifies that protection depends on the coating method, article design and service environment and notes that duplex systems (sherardized + organic coating) are covered by other standards.

Key topics and technical requirements

• Sherardizing process: thermal diffusion in a slowly rotating closed container using zinc dust (300 °C–500 °C; normally below zinc’s melting point of 419 °C). Coatings formed are zinc/iron alloys.
• Coating thickness: commonly achievable from about 10 µm to 75 µm (or more as required); thickness controlled by zinc amount, time and temperature.
• Container size limitation: typical sherardizing containers ~2000 × 480 × 400 mm - large assemblies may need to be processed unassembled.
• Surface preparation: grit blasting is preferred; surfaces must be free of oil, grease, rust, scale and lacquers. Alkaline degreasing must be dried prior to blasting or sherardizing. Acid pickling only in special cases.
• Design considerations: allow extra clearances for mating parts and threaded components to accommodate coating thickness. The standard lists recommended thread clearances (e.g., for 10 µm coating → 120 µm clearance; 75 µm → 900 µm).
• Special materials and components: guidance on springs, high‑tensile steels (prefer unassembled and processed at lower temperatures, e.g., 320–380 °C to protect temper), sintered parts and castings.
• Post‑treatments: conversion coatings (phosphating, chromating) are normally applied to produce passivated, dust‑free surfaces; organic topcoats (duplex systems) are outside the scope.

Practical applications

• Corrosion protection for small to medium metal parts with complex geometries (fasteners, small castings, springs, tubes).
• Industries: automotive components, construction hardware, oil & gas tubulars, fastener manufacturing, and general metal finishing operations.
• Useful for: design engineers, corrosion specialists, coating specifiers, sherardizing service providers and procurement teams specifying protective finishes.

Who should use this standard

• Design and manufacturing engineers preparing parts for sherardizing.
• Coating and corrosion engineers selecting protective systems.
• Spec writers and purchasers who need to define clearance, surface prep and coating classes for contract requirements.

Related standards

• ISO 17668 (coating classes / requirements)
• ISO 12944-5 and EN 13438 (guidance on duplex systems and organic topcoats)
• ISO 8044 (corrosion terminology)

Keywords: ISO 14713-3, sherardizing, zinc coatings, corrosion protection, duplex system, coating thickness, surface preparation, thread clearance.