Adhesion checks are most probably the best indicator of the condition of the powder.
The adhesion of a powder is usually tested by applying a normal coating on a panel at standard settings.
After a certain time interval, the panel is subjected to an impact of a controlled force, which is reproducible.
Adhesion tester for electrostatic powder enamel - Improved design for better clamping - Supplied complete with evaluation software
The adhesion strength may be calculated by means of the following formula :
Adhesion = ( powder weight after impact / powder weight before impact ) x 100 %
According to the theory, there are two different methods :
The only difference between the STPA and LTPA method is the duration of the time interval between powder application and impact. (1 minute versus 15 minutes)
|Test result||Conclusion according to DEV|
|STPA > 75 %||Very safe for the enamelling shop|
|75 % > STPA > 65 %||With risk for the enameling shop|
|STPA < 65 %||Insufficient for the enameling shop|
However, please note that in order to get reproducible results, it is necessary to keep the following test parameters constant :