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our thinking when trying to predict total process time to produce a desired coating thickness. Most of the time, we are interested in how long it will take to form a coating of a certain thickness at a given current density. Equation 2 allows us to estimate the amount of time to produce a given oxide thickness at a particular current density. We can compensate for the amount of oxide formed during the ramp by looking at Equation 4, and realizing that during the ramp, the average current density is half the final current density. Using Equation 2 or Table 1, we find that if we want to put on 1 mil of oxide at 30 ASF, it will take 24 minutes. So then we know that if we are doing MIL-SPEC anodizing to MIL-A-8625 and want to put on 2.0 mils, it will take 48 minutes anodizing at 30 ASF. What if we have a 10-minute ramp to the final current density? We can work succes- sively through Equation 4 to deal with the ramp and then use Equation 2 to predict how long we have to run at full current density to achieve our target thickness of 2.0 mils. From Equation 4: where the final current density is 30 ASF and the ramp time is 10 minutes. We want a final thickness of 2.0 mils, therefore our dwell time must produce: 2.0-0.2083 = 1.7917 mils. Using Equation 2, we calculate how long to anodize at 30 ASF to produce 1.7917 mils: To summarize this example, a ramp of 10 minutes to 30 ASF with a dwell time of 43 minutes at 30 ASF will produce 2.0 mils of oxide to a good approximation. If one is comfortable with Equation 2 and the fact that, during the ramp, the effective current density is half that during the dwell period (Equation 4), there is a simpler way to predict the amount of time required to ramp and dwell: A. Use Equation 2 to predict the dwell time required to produce the coating thickness desired at the proposed current density. B. Subtract half the ramp time from the prediction in Equation 2, and use that as the ramp compensated dwell time. Mathematically, a 10-minute ramp from zero to full dwell current produces the same effect as a five-minute dwell at full current. Here's an example of a Type II anodize run worked problem: Say an anodizer wishes to run Type II and then dye the parts a deep black color. He or she might decide to run at 12 ASF to a thickness of 1 mil. For various reasons—part configuration, racking density and so on—the anodizer chooses a six-minute ramp. How long does the anodize need to dwell so that the final thickness is 1.0 mil? Equation 2 or Table 1 shows us that at 12 ASF, 60 minutes are required. Our six-minute ramping from zero to full current is equivalent to three minutes at full current density. Therefore, 60 – 3 = 57 minutes of dwell at 12 ASF are required after the six-minute ramp in order to achieve a 1.0-mil oxide thickness. WEBB-STILES offers more than 60 years of practical expertise in the Overhead Conveyor and Custom Engineered Conveyor Systems. Whether you are looking for a new system or having problems with a current system, contact a WEBB-STILES Sales Engineer for all your Conveyor needs. Valley City, Ohio Corporate Sales / Engineering / Manufacturing Gadsden, Alabama Webb-Stiles of Alabama Sales / Engineering / Manufacturing Webb-Stiles of Canada Sales Toronto, ON Ph: 330-225-7761 Ph: 888-272-3815 Ph: 256-492-6642 Bibliography Westre, S.G. 1997, 2017. Anodizing Best Practices and Troubleshooting. Training Manual, Minden: Chemeon Surface Technology. Westre, S.G. 2000. Anodizer's Reference Manual. Training Manual, Minden: Chemeon Surface Technology. Runge-Marchese, J.M. 1999. Electrochemical deposition of a composite polymer metal oxide. United States of America Patent 5,980,723. November 9. Chesterfield, L. 2008. Calculating Anodizing Rate for Type II and Type III Coatings. PLATING C L I N I C PRODUCTS FINISHING — PFonline.com 75 Thickness during ramp= * CD*t A*min ft²mil 720 1 2 = * 30*10 720 1 2 = 0.2083 mils t(minutes)= Thickness CD A*min ft²mil * 720 = 1.7917 30 * 720 = 43.00 min.