Method for measuring NaNO2 concentration in phosphating solution

Abstract

The invention relates to the field of chemical detection, in particular to a method for measuring NaNO2 concentration in phosphating solution. The method for measuring the NaNO2 concentration in the phosphating solution carries out measurement by adopting communication of a liquid reaction device and a measurement device under constant temperature, and comprises the following steps: placing the phosphating solution and a magnetic stirrer in a sample bottle, placing sulfaminic acid solution in a liquid storage pipe, placing purified water in a water storage pipe, and well arranging devices; firstly placing a three-way valve in a three-way state, aligning liquid levels of the liquid storage pipe and a liquid measurement pipe, and recording the liquid level height H1 of a gas measurement pipe; then placing the three-way valve in a two-way state, communicating the reaction device and the measurement device, opening an electromagnetic stirrer to stir the solution, opening a dropper passage and dripping the sulfaminic acid solution into the sample bottle until no bubble generates; adjusting an adjusting knob to align the liquid levels of the liquid storage pipe and the liquid measurement pipe again, and recording the liquid level height H2 of the gas measurement pipe; and calculating the difference of the liquid level heights H1 and H2 as a volume number of N2, and then calculating the NaNO2 concentration.

Description

technical field [0001] The invention relates to the field of chemical detection, in particular to a method for measuring NaNO in phosphating solution 2 method of concentration. Background technique [0002] NaNO 2 It is one of the most commonly used phosphating accelerators. NO among them 2 - It can speed up the phosphating reaction at room temperature and improve the compactness and corrosion resistance of the phosphating film. NO 2 - The oxidizing property is very strong. If the amount is too much, it will passivate the surface of the steel, hinder the phosphating reaction, and a blue film will appear. NaNO 2 It is unstable in acidic phosphating solution, easy to decompose, and needs to be replenished continuously. When the concentration is lower than the lower limit, it is difficult to form a continuous phosphating film, and even the appearance of the phosphating film is yellowed and rusted, so NaNO 2 Concentration is a main factor affecting the quality of phosp...

AI Technical Summary

Problems solved by technology

[0007] When using a fermentation tube to measure nitrite, since the degree of mixing of solid sulfamic acid and phosphating solution in the straight tube is not the same for each operation, the speed of gas generation and the discharge speed of the solution in the straight tube cannot be guaranteed to be consistent. At the same time, the gas is continuously generated and gathered on the top of the straight tube, so that the solution in the straight tube is continuously discharged, and the volume is continuously reduced, but it cannot guarantee that the nitrite in the phosphating solution can all react with the solid sulfamic acid at the bottom of the fermentation tube; And it is greatly affected by the amount of sulfamic acid added, so the results measured by the sulfamic acid method carried out with fermentation tubes are difficult to be accurate

In the actual measurement, the results measured by different operators are often inconsistent, the repeatability is poor, and the error is about 10%.

Images