[sswee]

After writing this, I went back over everything and found the problem and where the .95 ohms came from. It was in a calculation step I had been skipping because I already new the answer. I hope there is still something in here you can use. SS

1. How come when I plug my criteria into the 720 calculator located HERE, the calculator shows that my PAR occurs at 30 volts? Do I not have the correct formula for calculating PAR? There is quite a difference between 11.4 and 30 volts!

The 30V is arrived at from Fibergeeks tests which determined the average ohms per square foot to be 2.5 ohms. A CD of 12 ASF x 2.5 ohms per square foot = 30V peak voltage. The tests were run at a 3:1 acid ratio.

2. I've read and read that just because PAR is reached, the anodizing may not be complete. Several things such as electrolyte temperature and agitation may allow PAR to be reached prematurely. I assume that if the working parameters are held constant (electrolyte concentration, temperature, agitation, ect...) that in theory PAR should be achieved at the same time as the calculated Anodizing Duration (my last formula, taken from the 720 rule)?

PAR does not coincide with the anodizing duration calculated by the 720 rule. The 720 rule calculates a run duration based on a desired coating thickness. It is true that PAR is sometimes reached before a run duration is complete. This is due to the enlargement of the pore size even though the coating continues to grow in thickness. If all the parameters were held constant, then PAR would be achieved at approximately the same time on different runs of the same material type. Different materials have different voltage curves under the same parameters. All the runs I have made confirm this.

3. Is it possible to calculate the anodizing duration required using PAR? If so, how?

Not to my knowledge. You can anodize according to PAR but I don't see how it could be calculated with so many parameters to figure in. The results I achieved running by par were not consistent by any means. I was told it was due to the accuracy of the equipment I have.

5. I also understand that some of you wait for the voltage to drop by 10-12% from PAR thus indicating that the dissolution is beginning to overtake the creation of the anodic layer. Is this recommended? I realize that some dissolution is a good thing - is this why this method is recommended?

Yes because the enlargement of the pore size is causing the drop in resistance even though the thickness of the coating still grows.

6. In the PAR formula (PAR = 0.95 / Surface Area x Total Current) I realize that 0.95 represents 0.95 Ohms per 1 square foot. I am also aware that temperature and agitation will alter the resistance, however, is this resistance of 0.95 Ohms proportional to the current density utilized or the alloy being anodized? If so, is it enough to be concerned about?

Where did you get the figure of .95 ohms? It is not familiar to me at this moment. According to my understanding, the resistance per foot squared is proportional to all the parameters of the circuit but not enough to be concerned with. If I can remember how it was told to me, The value of PAR is inversely related to the size of the part. This is another reason calculating anything by PAR would be difficult.
The way I was taught to calculate everything before there was a calculator is the same as the calculator gives. Maybe something is off on the calculator you have. If anyone wants a copy of the calculator on MS Excel or the other one just email me and I'll send you a copy.
Sorry if some of this is not clear. It is in my head but hard for me to sometimes convey to another.
SS