（1） Test steps
Soak solvent solution (already at room temperature) – first step
1. Weigh the quality of phosphating steel plate (0.001g, accurate, as shown in W0)
2. Submit the paint film sample (conventionally, cured in a dryer, placed in the dryer, and weighed. W1 (mil gram accurate) (3×0.001).
3. 24 h (room temperature) in the corresponding mixed solvent (shaking)= sample and filter paper washing (the surface shows about wiping the remaining solvent)
4. The sample was then dried using the oven at 105 ℃ for 30 minutes which was after removing from the oven and cooled in the dryer system until it achieved room temperature which before cooling unit. Then, it is placed on a precision scale (0.001 g) and recorded as W2 (densimeter mass + solution mass + precipitate mass + air).