影响盐雾试验结果的决定因素

影响盐雾试验结果的决定因素

（Determining factors affecting the results of salt spray test）

1、盐溶液的浓度及密度（1, the concentration and density of the salt solution）

盐溶液的浓度对腐蚀速度的影响与材料和覆盖层的种类有关。浓度在5%以下时钢、镍、黄铜的腐蚀速度随浓度的增加而增加；当浓度大于5%时，这些金属的腐蚀速度却随着浓度的增加而下降。上述这种现象可以用盐溶液里的氧含量来解释，盐溶液里的氧含量与盐的浓度有关，在低浓度范围内，氧含量随盐浓度的增加而增加，但是，当盐浓度增加到5%时，氧含量达到相对的饱和，如果盐浓度继续增加，氧含量则相应下降。氧含量下降，氧的去极化能力也下降即腐蚀作用减弱。但对于锌、镉、铜等金属，腐蚀速度却始终随着盐溶液浓度的增加而增加。

The influence of the concentration of the salt solution on the corrosion rate is related to the type of the material and the covering layer. The corrosion rate of steel, nickel and brass increased with the increase of concentration in the concentration of 5%. When the concentration was greater than 5%, the corrosion rate of these metals decreased with the increase of concentration. This phenomenon can be explained by the oxygen content in the salt solution, salt solution, the oxygen content and salt concentration, in the low concentration range, the content of oxygen increased with the increase of salt concentration, however, when the salt concentration increased to 5%, the oxygen content reached the relative saturation, if the salt concentration continues to increase, the oxygen content decreased correspondingly. The oxygen content is decreased, and the depolarization ability of oxygen is decreased, and the corrosion effect is weakened. But the corrosion rate of zinc, cadmium, copper and other metals increased with the increase of the concentration of the salt solution.

2、样品的放置角度及位置（2. The position and angle of the sample）样品的放置角度对盐雾试验的结果有明显影响。盐雾的沉降方向是接近垂直方向的，样品水平放置时，它的投影面积最大，样品表面承受的盐雾量也最多，因此腐蚀最严重。研究结果表明：钢板与水平线成45度角时，每平方米的腐蚀失重量为250 g，钢板平面与垂直线平行时，腐蚀失重量为每平方米140 g。GB/T2423.17-93标准规定“平板状样品的放置方法，应该使受试面与垂直方向成30度角。

The results of salt spray test have obvious influence on the sample placement angle. Salt spray deposition direction is close to the vertical direction, when the sample level is placed, it is the largest projection area, the amount of salt spray on the sample surface is also the most, so the most serious corrosion. The research results show that: when the steel plate and the horizontal line is 45 degree angle, the corrosion weight loss per square meter is 250 g, the steel plate plane is parallel to the vertical line, and the corrosion weight loss is 140 g per square meter. The GB/T2423.17-93 standard provides for the placement of the plate like specimen, which should be the 30 degree angle of the tested surface and the vertical Fang Xiangcheng.

3、试验的温、湿度（3, the test temperature, humidity）

温度和相对湿度影响着盐雾的腐蚀效果作用。一般金属腐蚀的临界相对湿度大约为70%。当相对湿度达到或超过这个临界湿度时，盐将潮解而形成导电性能良好的电解液。当相对湿度降低，盐溶液浓度将增加直至析出结晶盐，腐蚀速度相应降低。

试验温度越高盐雾腐蚀速度越快。国际电工委员会IEC60355：1971《AN APPRAISAL OF THE PROBLEMS OF ACCELERATED TESTING FOR ATMOSPHERICCORROSION》标准指出：“温度每升高10℃，腐蚀速度提高2～3倍，电解质的导电率增加10～20%”。这是因为温度升高，分子运动加剧，化学反应速度加快的结果。对于中性盐雾试验，大多数学者认为试验温度选在35℃较为恰当。如果试验温度过高，盐雾腐蚀机理与实际情况差别较大。

The effect of temperature and relative humidity on the corrosion of salt spray. The critical relative humidity of general metal corrosion is about 70%. When the relative humidity reaches or exceeds the critical humidity, salt deliquescence formed good conductive properties of electrolyte. When the relative humidity is decreased, the concentration of the salt solution will increase until the precipitation of crystalline salt, the corrosion rate will be reduced accordingly.

The higher the temperature is, the faster the salt spray corrosion rate is. "Every 10 degrees Celsius rise in temperature, corrosion rate is improved by 2 ~ 3 times, the conductivity of the electrolyte increased 10% ~ 20%" point to, according to the International Electrotechnical Commission IEC60355:1971 "of an APPRAISAL the on of ACCELERATED testing for ATMOSPHERICCORROSION". This is because the temperature increases, the molecular motion is intensified, the chemical reaction rate is accelerated. For the neutral salt spray test, most scholars believe that the test temperature is more appropriate at 35. If the test temperature is too high, the corrosion mechanism of the salt spray is different from the actual situation.

4、盐溶液的pH值（4, the pH value of the salt solution）

盐溶液的pH值是影响盐雾试验结果的主要因素之一。pH值越低，溶液中氢离子浓度越高，酸性越强腐蚀性也越强。以Fe/Zn、Fe/Cd、Fe/Cu/Ni/Cr等电镀件的盐雾试验表明, 盐溶液的pH值为3.0的醋酸盐雾试验(ASS)的腐蚀性比pH值为6.5～7.2的中性盐雾试验(NSS)严酷1.5～2.0倍。

由于受到环境因素的影响，盐溶液的pH值会发生变化。为此国内外的盐雾试验标准对盐溶液的pH值范围都作了规定，并提出稳定试验过程中盐溶液pH值的办法,以提高盐雾试验结果的重现性。

PH value of salt solution is one of the main factors that affect the results of salt spray test. The lower the pH value, the higher the hydrogen ion concentration in the solution, the stronger the acidity, the stronger the corrosion resistance. To salt fog testing of Fe / Zn, Fe/Cd, Fe/Cu/Ni/Cr, such as electroplating showed that salt solution of pH values of 3.0 acetic acid salt spray test (ASS), corrosive than pH value is 6.5 ~ 7.2 neutral salt spray test (NSS) 1.5 harsh ~ 2.0 times.

Due to environmental factors, the pH value of the salt solution will change. So at home and abroad of the salt spray test standard of salt solution pH range are specified, and puts forward methods of stability test process of salt solution pH value, in order to improve the reproducibility of results of salt fog test.