| abstract |
The solution to be stored in the treatment tank is agitated so that the average acceleration (a) represented by the following equation is 8 cm / sec 2 by the vibration stirring means provided in the treatment tank within the range of immersing the metal moldings or substantially around the horizontal surface of the metal moldings do:n n n [Equation 1]n n n n n n n n In this formula,n n n X, Y, and Z are average accelerations of the velocity changes within 60 seconds measured simultaneously in three axes X, Y and Z perpendicular to each other at the measurement location in cm / sec 2 . |