Post Overview

Hot-dip galvanized steel components primarily exhibit the following corrosion characteristics:

Intact Zinc Coating Condition

When the galvanized surface remains undamaged, only zinc corrosion occurs.

Zinc corrosion products form a protective layer, significantly slowing the corrosion rate.

Service life is 15-30 times longer than uncoated steel components.

Metallurgical Bonding Advantage

The hot-dip process creates a metallurgical bond between the zinc coating and steel substrate, ensuring complete coverage.

This unique feature provides exceptional mechanical damage resistance during processing, storage, transportation, and installation.

All surfaces – including interiors, exteriors, corners, and narrow gaps – receive full zinc protection.

Localized Coating Damage Scenario

Most commonly, scratches or mechanical damage expose underlying steel.

Unlike non-metallic coatings, galvanized steel exhibits sacrificial protection:

Zinc (anode, -1.05V) corrodes preferentially to iron (cathode, -0.036V) in moist environments.

Dense zinc corrosion products dramatically slow further reaction rates.

This electrochemical mechanism, called cathodic protection, significantly enhances overall corrosion resistance.

Critical Importance of Coating Adhesion

Corrosion typically initiates at areas with poor zinc-substrate adhesion rather than through uniform thinning.

Adhesion quality outweighs coating thickness in determining service life:

Weak interfacial bonding points become failure origins (analogous to the "bucket effect").

Even thick coatings fail prematurely if adhesion is locally deficient.

This principle is essential knowledge for hot-dip galvanizing technicians.

Technical Notes:

Standard electrode potentials: Zn (-1.05V) vs. Fe (-0.036V)

The sacrificial protection mechanism ceases when zinc is fully consumed at damaged areas.

This translation maintains all technical nuances while optimizing readability for engineering documentation. The structured presentation facilitates quick comprehension of key corrosion mechanisms.