Continuous Galvanizing Line: Coating Quality

Coating defects and warranty claims traced back to solution temperature, not the brushes. A continuous galvanizing line producing coil for demanding surface applications was getting three to four months of brush life and fighting fish eyes and uncoated spots. The customer suspected the brushes. The survey pointed to solution temperature.

Coating defects and short brush life

A continuous galvanizing line producing coil for demanding surface applications was experiencing fish eyes, uncoated spots, and a growing number of warranty claims. Brush life averaged three to four months, which added downtime and maintenance cost. Management wanted to find the root cause.

Discovery

The customer initially suspected a brush issue. In the first conversations, Felton MBC saw a broader pattern that pointed to process problems rather than isolated brush failures, and an on-site engineering survey was scheduled.

Engineering Survey

Felton MBC conducted a full line walkdown, a consumable review, and a solution analysis. The survey produced four findings, with solution temperature at the top of the list.

01. Solution temperature was unstable and below target

Cold cleaning solutions are more viscous, which makes them clean less effectively and lets more contamination carry over into downstream sections of the line.

02. Soil loading was several times above recommended levels

Suspended solids in the cleaning solution measured several times higher than recommended operating levels, more than the cleaning system was designed to handle.

03. Spray header positioning trapped contaminants

The spray pattern left contaminants in the brush-strip contact area instead of removing them from the process.

04. Brush construction was mismatched to operating conditions

The existing brushes did not have enough filament density for the contamination levels on the line.

Recommendations

Felton MBC delivered a prioritized improvement plan that included heat exchanger upgrades, improved filtration, spray header repositioning, and higher-density brushes with upgraded filament specifications.

Capital funding for the filtration improvements was not immediately available, so Felton MBC developed an interim strategy to keep contamination levels in check until the permanent upgrade could be installed.

Implementation

The customer upgraded the heat exchangers, stabilized solution temperatures, put the interim contamination controls in place, and installed the recommended brush system.

Results after implementation

Brush life increased from 3 to 4 months to 12 to 15 months
Fish eyes and uncoated spots declined significantly
Warranty claims decreased
Unplanned brush-related outages became uncommon

“It’s easier to heat water than mud.”
Jimmy Mitchell, Senior Steel Mills Engineer, Felton MBC

Key takeaway

The root cause was solution temperature, not the brushes. Cold cleaning solutions are more viscous and less effective, and they let contamination carry through to the strip. Once the temperature stabilized and the interim filtration controls were in place, brush life roughly quadrupled and the coating defects behind the warranty claims declined with it.

Official Disclaimer

The information contained in this document is based on tests which are believed to be reliable. Since actual conditions of use may vary and are beyond the control of FELTON the product's specified characteristics cannot be guaranteed and are offered solely for the buyer's evaluation and verification. There are no warranties, representations or conditions, expressed or implied, of any kind, including, but not limited to, merchantability or fitness for a particular purpose made by FELTON of its officers, employees or affiliates, in connection with the sale of the products described in the document. Accordingly, the purchaser and each user assumes all risks and liability in connection with their use of such products. Nothing contained herein is to be construed as permission, recommendation or inducement by FELTON to use any product or process so as to infringe or conflict with any patent. Further, it is the user's obligation to utilize this material in full compliance with health, safety and environmental regulations.