Phosphate Neutralizer 12
Why is the use of a neutralizer between the phosphate coating and the application of a lubricating topcoat beneficial?
- Neutralization: The buffered alkalinity (around pH 9.2 in a new working bath) will neutralize acid residues left on the coil upon exiting the phosphate rinse. Both stearate lube and polymer baths are sensitive to changes in pH. A typical stearate runs at a near neutral pH, while polymer in a range of 8.5-9.5. The drag in of any acidity will adversely affect the performance of these topcoats in subsequent drawing or heading operations.
- Prevention of Cross Contamination: The use of Phosphate Neutralizer 12 will reduce the amount of metal contamination being dragged into topcoat baths, thus increasing tank life. Both zinc and iron are contaminants in a reactive lube bath – in one case, the addition of a neutralizer step to the cleaning house process prevented metal build up in the lube and increased the dump schedule from every 8-12 weeks to 26 weeks!
- Corrosion Protection: A rust inhibitor is incorporated into the Phosphate Neutralizer 12 formulation which has been proven both in the laboratory and in the field to prevent corrosion during transit or when warehousing coated product. This added protection is extremely beneficial during the humid months of summer.
In the Laboratory: A series of test panels were zinc phosphate coated, rinsed, dipped in Phosphate Neutralizer 12 at either 0.5 or 1.0 oz./gallon and then either a polymer (5% solids) or a reactive stearate lube (1.2 Babcock) was applied. The test panels were then subjected to 100% Relative Humidity (ASTM D-2247). The test panels were checked for signs of red rust every 24 hours. Panels at both neutralizer concentrations survived between 312 – 336 hours of exposure…that’s 2 weeks with no corrosion.
In the Field: A Heatbath customer located in New England was having rusting issues on coated product in their warehousing facility located in the Midwest. The problem was reported in mid-July. Over 50% of product was showing signs of red rust. Immediate action was taken…
A spare tank was placed online and Phosphate Neutralizer 12 was charged at 1 oz./gallon. Initially, there was no heat in this tank, but considering the situation; it was a place to start. After phosphate coating, the coils were rinsed and then dipped in the Phosphate Neutralizer 12 for 30-60 seconds prior to the reactive lube topcoat. Within the month the rusting issues were reduced and have since remained at less than 1%. Heat was added to the tank and operating temperature is 160°F. The Phosphate Neutralize 12 is dumped and recharged on a weekly schedule.
Maintenance of the Phosphate Neutralizer 12 Bath: Because the Phosphate Neutralizer 12 bath is a sacrificial tank used to neutralize any acidity and remove any residual zinc not rinsed entirely after phosphating, most companies will dump this bath and recharge on a calendar or tons processed basis. Depending on your workload and more importantly on the cleanliness of your rinse tanks, the Phosphate Neutralizer 12 may have to be dumped weekly, every 2 weeks or once a month. Heatbath can help you to determine this schedule through sample analysis.
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