Causes and Solutions for Flaking PPGI Steel Coatings

The structure of PPGI steel includes galvanized, chemically converted, and painted layers (primer + topcoat). Premium PPGI has a corrosion resistance of 15-30 years, and the rate of coating peeling is less than 3% in the course of use. If your purchased PPGI has the problem of coating flaking in a short period, you can find out the reasons from the coating technology, product packaging, storage environment, and so on.

PPGI Steel - Flaking — PPGI Steel – Flaking

Main Reasons for PPGI Coating Flaking

Poor quality of the substrate: The zinc coating on galvanized steel is insufficiently thick, less than 60 g/m2 on both sides.

Inadequate pre-treatment of the substrate: The surface of the galvanized steel is not cleaned of residual oil, grease, oxides, or dust during the cleaning process, which results in reduced adhesion of the coating.

Chemical conversion layer not formed: Uneven phosphating/passivation of galvanized steel does not result in the formation of an effective protective film, leading to weak bonding of the primer to the zinc layer and poor adhesion of the coating.

Unsophisticated coating process: Insufficient adhesion of the paint to the substrate (galvanized steel) during the coating process, as well as unstable paint formulations, can lead to flaking of the coating.

Improper curing process: Insufficient baking temperature or too short a time (e.g., PMT temperature is too low), resulting in incomplete cross-linking of the coating.

Mechanical damage: Excessive bending and stamping during processing can lead to localised coating loss of PPGI steel. Collisions and scratches during transport can also cause the coating to crack and peel off.

Preventing PPGI Coating Flaking Solution

Purchase of raw materials: Purchase of substrates complying with international standards such as ASTMA755, EN 10346, JIS G3321.

Optimization of pre-treatment steps: Enhancement of the degreasing process and optimization of the phosphating treatment during the treatment of galvanized steel.

Upgrading of the coating system: Adoption of a high adhesion epoxy primer, adjustment of the coating speed and curing temperature.

Adoption of high-performance coatings: Increase the thickness of the galvanized steel in corrosive environments and select high-weathering paints such as PVDF, SMP, and HDP.

Improve packaging: Use anti-scratch packaging to reduce transport damage.

Improve processing: Use specialized tools for further processing of PPGI steel.

PPGI Steel Precautions

PPGI coating peeling is one of the reasons affecting the service life of PPGI steel. In addition to improving the production and processing technology, reasonable maintenance should be carried out during installation to ensure the stable performance of PPGI steel.

PPGL PPGI Factory - Production — PPGL PPGI Coils

Avoid open storage, and control the humidity of PPGI steel storage environment to less than or equal to 70%.
Use special tools for coating when cutting and punching.
Avoid welding directly on the coated surface.
Regularly check the integrity of the coating in highly corrosive environments such as chemical plants.
Avoid excessive bending and leave expansion joints when producing corrugated boards and roofing sheets with PPGI.

Maintenance of PPGI Steel Coil and Sheet

Rinse the surface of PPGI products regularly with a neutral detergent.
Inspect PPGI coatings annually for pinholes and scratches.
Repair any localised flaking with paint.
PPGI surface can be sprayed with anti-rust wax to increase corrosion resistance.

The above are the possible causes and solutions for the flaking of PPGI steel, as well as recommendations for the maintenance and use of PPGI material. If you are planning to purchase a premium PPGI coil sheet with non-peeling coating, welcome to contact Wanzhi Group! Wanzhi has a proven coating technology, our hot-dip galvanizing, roll coating, baking, and curing processes are advanced, and we are experienced in exporting and customizing cost-effective PPGI solutions for a wide range of applications.