Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

February, 2007

Calculating Paint Coverage Rates

Q: 1. I'm interested in knowing if you have an industry standard or a parameter range that would indicate standard painting speeds and feeds, assuming an automtic (robotic) paint line? I fully underestand there's alot of variables here: gun type, paint type, tip aperatures, ect. However, I'm really looking for a general rule of thumb for how much paint coverage (lets say using PU paint) can be achieved/mil at a standard feed rate in/min (or mm/min). It would be nice to have some kind of correlation or time association between the specified thickness and coverage per sq in. For example, at a robot speed of 20ipm the paint coverage is 20um per sq in or whatever it happens to be. Any input is greatly appreciated.

2. It appears that a general rule is 1 solid gal. of paint covers 1604 sq ft at .001" thick. Can I apply this constant with a paint mixture (base coat+thinner+ hardner)?

A: Off-hand I don't have coverage rates that relate to the speed of the robot; however, the general algorithm for calculating coverage is:

Coverage (ft2) = 1604 ft2/gal/mil x Gals x % Volume Solids x % Transfer Efficiency
                                                     Dry film thickness (mils)

This algorithm applies to all paints, regardless of their mixture with or without thinners. To use the calculation you do need to know the % volume solids of the coating and the transfer efficiency (TE). With regard to the TE you can conduct online tests to determine this value, or if you don’t have the luxury of conducting tests you must guess.

I have not calculated the coverage rate as a function of time, but it is not too difficult to add a time dimension to the algorithm. First, you need to experimentally determine the fluid flow rate (g/min) or (mL/min) and then you need to know the % Wt. solids of the coating and possibly also its density (g/L) or (lbs/gal).  The required input data depends on how you measure your fluid flow rate; by weight or volume.

Hope this helps.


Ron Joseph

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