Dear Unni, I think that you are trying to determine the cost of powder per surface area covered. There is a simple conversion to calculate how many square feet a pound of powder will cover at a given film thickness. Take 192 and divide by the specific gravity of the powder. This will give you the theoretical number of square feet a pound of powder will cover at 1.0 mil thickness and 100% efficiency. Powders typically are applied at approximately 2.0 mils, and the efficiency can range from 50 to 95%.
For example: 1.0 lb of a powder with a 1.6 specific gravity theoretically will cover 60 ft2 at 2.0 mils. (192 divided by 1.6, then divided by 2.0 mils). Estimating an efficiency of 65%, you could expect to cover around 39 ft2/lb.
If you are paying $3/lb for this powder, then your material cost per square foot would be approximately $0.077. Of course this doesn’t take into account any of your overhead costs such as labor, energy, building, utilities, equipment depreciation or ancillary supplies.
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Dear Joe, We are using tap water in our pre-cleaning and rinse bath. I have heard that we should be using DI water. What is your take? --Craig
Hi Craig, If you want any kind of corrosion resistance you should switch your final rinse in your precleaning system from tap to DI (deionized) water. Tap water can contain varying amounts of impurities, such as water soluble salts, that act as propagation points for corrosion.
The rinse after your alkali cleaning stage can be a tap water rinse as long as you keep it clean. This is usually accomplished by overflowing it to keep the concentration of drag-in from the previous process low.
DI water can be obtained through a reverse osmosis or ion exchange process.
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