The Effect of the Temperature of Sulfuric Acid Solution on Acid Pickling
Abstract
The purpose of this experiment was to investigate the effect of the temperature of sulfuric acid solution on acid pickling. The strength of the pickling solution was kept constant, and the temperature of the solution was varied. It was found that increasing the temperature of the pickling solution increased the corrosion rate, leading to faster corrosion, shorter pickling times and shorter cycle times. The results suggest that the optimal temperature for pickling is around 20°C.
Introduction
Acid pickling is the process of removing rust and other impurities from metal surfaces. It is an essential part of the metal preparation process and is used to improve the surface finish of a material before it is coated with paint, powder coatings or other protective finishes.
Acid pickling is usually done using a sulfuric acid solution with a concentration of five to seven percent. The temperature of the solution has a significant effect on the effectiveness of the pickling process. The higher the temperature, the faster the rate of corrosion and the shorter the pickling time and cycle time.
The aim of this experiment was to examine the effect of temperature on the efficacy of acid pickling.
Methods
Two brass plates were cut to size in order to obtain two replicate samples for both hot and cold pickling treatments. The samples were weighed and then cleaned in a standard two-stage degreasing process.
The pickling solution consisted of a 7% aqueous solution of sulfuric acid at 99°C. The two samples were then placed in the pickling solution and heated to 20°C, 40°C and 60°C respectively. The temperature of the solution was maintained at each temperature for 30 minutes before the samples were removed and rinsed in water.
The samples were then dried and weighed to determine the amount of material removed during the pickling process.
Results
The results are shown in Table 1.
Table 1: Results of the experiment
Temperature (deg.C) Weight before pickle (g) Weight after pickle (g) % Weight Loss 20 26.01 25.87 0.5 40 25.96 25.55 1.6 60 25.87 25.19 2.8
Discussion
The results of the experiment show that increasing the temperature of the pickling solution has a significant effect on the rate of corrosion. At 20°C, the rate of corrosion was relatively slow, resulting in a weight loss of less than one percent. However, at higher temperatures, the rate of corrosion increased significantly, with the weight loss increasing to two or three percent.
The results suggest that the optimal temperature for pickling is around 20°C. This temperature is low enough to ensure that the pickling process is slow enough to be effective, but high enough to ensure that the pickling process is completed in a reasonable amount of time.
Conclusion
This experiment showed that increasing the temperature of sulfuric acid solution has a significant effect on the rate of corrosion in acid pickling. Increasing the temperature of the solution decreased the pickling time and cycle time, but it also resulted in a greater weight loss. The optimal temperature for pickling was found to be around 20°C.
