By Mike Manetta, Target Account Executive
When producing high-end aluminum and steel parts, such as those used in automotive manufacturing, there is no room for errors. A quality part must have a long, reliable shelf life. This means the part must have a durable metal coating that can resist corrosion. Pretreating aluminum and steel parts with an iron phosphate coating will increase the lifespan of a part as long as the weight of the iron phosphate is applied within the proper range. If the weight of the iron phosphate is too light, the part will not have an adequate corrosion barrier. If the weight is too heavy, the part may become brittle and cause cracking, or there may be loss of adhesion, which will diminish the longevity and durability of the part.
When it comes to the quality of your parts, neither a light nor a heavy coating weight is acceptable. There is one tried-and-true, scientific method you can rely on to test if the iron phosphate coating weight is within the proper range, known as the weigh-strip-weigh method.
Here are the four steps for testing with this method:
- Take a steel or aluminum panel (the same material as the part) and run it through the iron phosphate pretreatment.
- Weigh the panel in order to find the baseline weight.
- Once that is determined, dip the panel into a chromic acid bath, which will remove the phosphate coating from the panel.
- Weigh the panel again and subtract that weight from the baseline weight to find the phosphate coating weight.
If the weight is within the proper range, the chemical balance of your iron phosphate bath is within spec and is ready for use. If the weight is outside of the proper range, there is something out of balance with your iron phosphate bath. Examine all factors that could affect the weight such as the age of the bath, pH of the bath or time spent in the bath. Once you determine what is causing the weight to be out of range, you can correct and retest. This process should be repeated until the iron phosphate coating weight is within the proper range.
Iron phosphate coatings offer a variety of valuable properties to extend the service life and improve the performance of the parts being treated. Your coating supplier can help establish the correct weight range to ensure the parts have suitable corrosion protection and adhesion control.
Contact me at 317-879-2055 to help determine the proper iron phosphate weight range to keep your parts strong.