Measurement of film salt fog resistance

The salt spray resistance of the coating film can be measured according to the method in the national standard GB/T177l-91 "Determination of resistance to neutral salt spray of paint film". This standard applies to the determination of the salt spray resistance of paint films. The salt spray Test Chamber is used to control a certain temperature, salt water concentration and time for the test, and the grade is evaluated by the degree of damage to the appearance of the model.

(1) Materials and equipment

Refined table salt, distilled water

Precision pH test paper: pH6.1~7.5

Erlenmeyer flask: 150mL

Glass funnel: diameter 100mm

Balance: Sensitivity is 0.00lg

Nozzle-type salt spray box: control the salt spray settlement to 0.4~1g/(80cm2·h).

(2) Measurement method

Prepare 3.5% saline solution with distilled water and adjust the pH value to 6.5~7.2.

Select the base material and supporting primer according to the product standard, and make boards according to GB/T1765 "Determination of heat and humidity resistance, salt resistance, weather resistance (artificial acceleration) paint film preparation method".

Record the original condition of the sample before testing.

The longitudinal direction of the sample plate is 30° to the direction of salt spray settlement, and there is a certain gap between two adjacent sample plates, and the distance between rows is less than 7.5cm.

Start the equipment, and when the temperature in the box reaches 40°C ± 2°C, start to calculate the test time l. Spray for 15 minutes every 45 minutes. When not spraying, the relative humidity in the box needs to be kept above 90%. Check once every 48 hours for continuous testing. After the first check, check every 72 hours. After each check , the position of the template should be changed. Carry out the last inspection according to the number of times specified in the product standard. If there is no product standard inspection time, it can be determined according to the specific situation.

In the continuous test, it is necessary to check the nozzle frequently to keep the spraying normal. Salt water cannot be recycled.

(3) Sample inspection and rating

When checking, carefully remove the template. Rinse off the salt deposited on the surface of the sample with tap water, and quickly dry it with cold air (or dry it with a towel or filter paper). According to GB/T1740 "Paint Film Resistance to Moisture and Heat", check and grade.