GB/T 31927-2015Zinc and aluminum based coatings on steel sheets and strips—Determination of lead and cadmium contents—Inductively coupled plasma mass spectrometric method (English PDF)

7.4 Coatings stripping

Pure-zinc, zinc-iron, zinc-aluminum alloy coatings. place the specimen piece (see 7.1) into the beaker; add 50mL of stripping solution (see 4.7); the specimen is completely immersed in the solution at the room temperature; shake the beaker and flip the specimen from time to time, till the coating surface has no hydrogen evolution. Then wash the specimen; if necessary, use nylon brush to eliminate the loose attachments attached on the specimen surface; combine the lotion. After rapid drying of the specimen substrate, use balance to weigh the specimen substrate mass m2, accurate to 0.1mg. Transfer the solution into the volumetric flask, dilute to the mark, mix evenly, and work as the to-be-tested solution.

Aluminum-zinc alloy coating. place the specimen piece (see 7.1) into 250 mL PTFE beaker; add 50 mL of sodium hydroxide solution (see 4.5), 3 mL of hydrogen peroxide solution (see 4.6); heat at low temperature, during which flip the specimen; when the specimen surface is completely bright, take out the specimen; use small amount of water to wash, the lotion there shall be combined into the beaker; continue to heat for 5min, take off and cool. After rapid drying the specimen substrate, use balance to weigh the specimen substrate mass m2, accurate to 0.1mg. Add 20 mL of hydrochloric acid (see 4.1) to the solution, after cool off to the room temperature, transfer the solution into a volumetric flask; dilute to the mark, mix evenly, and work as a to-be-tested solution.

7.5 Drawing a calibration curve

Take seven 100 mL volumetric flasks; add the same amount of reagent during the specimen treatment period, and appropriate amount of zinc standard solution (see 4.10) and aluminum standard solution (see 4.11) used for matrix matching; so that the content of zinc and aluminum is equivalent to that in the test solution. Add the standard solution of the measured elements in seven 100 mL volumetric flasks according to Table 1 and 2; dilute with water to the mark, mix evenly. Measure the strength of standard series solution, minus the strength of calibration solution with zero concentration, then obtain the net strength; draw the calibration curve with concentration of to-be-measured elements (µg/mL) as the x-axis, while the corresponding net strength of to-be-measured elements as the y-axis. […]