Galvanized steel sheet is widely used for air cooler casing. Zinc layer protects base steel from corrosion, yet white rust may form under high humidity conditions. White rust is zinc oxide and zinc hydroxide deposits. It appears as powdery white substance on galvanized surface after long contact with moist air. Xindacool carries out passivation treatment on galvanized parts after cutting and bending, forming a compact protective film on zinc surface. Passivation seals micro pores on zinc coating. Without this treatment, condensed moisture reacts with zinc and generates white rust rapidly. White rust itself does not immediately damage base steel. Heavy accumulation gradually consumes zinc layer and exposes raw steel substrate. Packaging protection during transportation matters. Water trapped inside packing crate creates humid microenvironment and triggers white rust before installation. After on-site installation, wipe off surface dust and avoid standing water staying on casing surface. Water droplets are the main trigger for white rust. Acidic cleaning agents must not touch galvanized casing. Acid erodes zinc coating and destroys passivation protective film quickly. If light white rust already appears, neutral cleaning solution can remove powder deposits. Then reapply supplementary passivation coating. Seafood cold storage needs extra attention. Salt vapor accelerates zinc coating degradation even with passivation treatment. Visual inspection for white rust shall be arranged in annual maintenance, focusing on bottom edge and welding seams of casing.
Q: What is white rust on galvanized casing? A: Powdery zinc oxide and hydroxide formed when zinc layer reacts with humid air. Q: What function of galvanized surface passivation? A: Build compact protective film and seal micro pores to reduce white rust generation. Q: Will light white rust immediately corrode base steel? A: No, heavy continuous rust consumption will finally expose steel substrate. Q: Why avoid acidic cleaner on galvanized surface? A: Acid destroys passivation film and rapidly erodes the protective zinc coating. Q: How to handle slight white rust? A: Clean powder with neutral solution and add supplementary passivation coating. Q: Where is white rust most likely to appear on casing? A: Casing bottom edges and welding seams where moisture easily accumulates. Q: How does sea salt vapor affect galvanized sheet? A: Salt speeds up degradation of zinc layer and passivation film. Q: What causes white rust before installation? A: Moisture trapped inside packaging box during transport and storage.
Address: No. 866, Putian Avenue, Sanjiang Sub-district, Shengzhou City, Zhejiang Province
Mobile phone: +86 13567599011
Landline: 0575-83268796
Email:michelle@xindacool.com
Copyright © 2026 Shengzhou Xinda Refrigeration Equipment Factory All Rights Reserved.