Ineffective Cleaner
We can clean hot-rolled P&O; on that material the slimiest, oiliest stuff cleans just fine, but the seemingly cleaner CRS will not clean up with our alkaline cleaner. We are water break-free after phosphate because of the acidic nature of the stage, but two things are happening: One, we are compromising the effective stage dwell time of our third stage because it has to clean before it can deposit phosphate, and two, we are trashing our third stage with an excess amount of soils.
Share
Q. I have a five-stage wash with conventional pretreat chemistry: alkaline clean, rinse, iron phosphate, rinse, rinse.
This past season we have suddenly found ourselves at the mercy of cold-rolled sheet steel. We can clean hot-rolled P&O; on that material the slimiest, oiliest stuff cleans just fine, but the seemingly cleaner CRS will not clean up with our alkaline cleaner.
Featured Content
We water break after the cleaner stage, and our phosphate stage has to finish the job. We are water break-free after phosphate because of the acidic nature of the stage, but two things are happening: One, we are compromising the effective stage dwell time of our third stage because it has to clean before it can deposit phosphate, and two, we are trashing our third stage with an excess amount of soils. D.O.
A. It is not unusual for the chemicals used in a washer to become ineffective as steel suppliers and manufacturing processes change over time. This is the reason you should have a very close relationship with your chemical supplier.
The supplier should constantly monitor the soils on your substrates and make adjustments to your process or chemicals to remove them. For instance, your cold-rolled steel may have paraffin -based soils on the surface. These require higher chemical temperatures, higher chemical strength, higher nozzle pressure, and so on to effectively remove them.
Furthermore, some soils are better removed with alkaline chemicals and some are better removed with acid-based chemistries. This is why most chemical suppliers use a “cleaner-coater” combination chemistry in the third stage to remove any soils left on the surface from the first (alkaline) stage. You can also increase the coating weight of the iron phosphate by increasing the chemical concentration in this stage. This will ensure that you will experience the same corrosion protection and coating adhesion as your other substrates.
RELATED CONTENT
-
The Powder Coating Process
Powder coating is one of the most durable finishes that can be applied to industrial manufactured products, and offers excellent corrosion protection and is very safe because of its lack of volatile organic compounds. To understand the powder coating process you should start with the fundamentals.
-
Preparation of Stainless Steel for Powder Coating
Should type 316 stainless steel castings be sandblasted before powder coating, or can they be chemically etched? Should the parts be pre-heated in an oven before coating?
-
Calculating the Cost of Powder Coating
How can you calculate the cost of powder coating a component if you only know its surface area? Powder coating expert Rodger Talbert has the answer.
