What are the methods of corrosion coupon testing
After the oil pipeline has been in use for a long time, the inside of the pipeline will be corroded, which requires the use of corrosion test tools to detect the degree of corrosion of the pipeline. So what are the test methods for corrosion coupon ? The editor below will explain in detail the method of corrosion sample test, I hope to help everyone. The details are as follows.
1. the weight method. The gravimetric method is simple and intuitive, suitable for laboratory and field trials. It is divided into two methods: weight gain method and weight loss method.
(1) Weight gain method. When the corrosion product adheres firmly to the sample, it is almost insoluble in the solution and is not contaminated by external substances. At this time, the degree of corrosion damage can be measured by the weight gain method. The weight gain method is suitable for assessing general and intergranular corrosion, but not for other types of localized corrosion.
(2) Weight loss method. The weightlessness method is a simple and straightforward method. It does not require the corrosion product to adhere firmly to the surface of the material, nor the solubility of the corrosion product, since all corrosion products must be removed from the sample after the test. The weight loss method directly indicates the weight of the material lost due to corrosion, and does not require analysis and conversion of the chemical composition of the corrosion product. These advantages of the weight loss method are widely used.
3. Corrosion product removal method. To properly evaluate the corrosion results, if the weight loss method is used, the corrosion products on the surface of the sample must be removed without damaging the metal substrate itself. It is impossible to completely damage the substrate at all, and only the damage is required to have no significant effect on the corrosion result. Different methods of removing corrosion products should be used for different metal materials and different corrosion products. There are three kinds of mechanical methods, chemical methods and electrolysis methods.
(1) Mechanical method Generally, rinse with tap water and scrub with rubber or hard brush, or scrape with wooden scraper or plastic scraper. Most of the loose corrosion products have been cleaned by this method. However, in order to completely remove the corrosion products to accurately test or inspect the local corrosion conditions, further chemical or electrochemical methods are required.
(2) Chemical method. A method of removing the corrosion product on the surface of the sample by dissolving a suitable chemical solution and operating conditions. In order to protect the metal matrix, a slow reagent is often added to the chemically removed solution. These methods are not complicated, but may damage the substrate during use, causing test errors; for this reason, blank samples of the same size of the same material that are not corroded should be cleaned under the same conditions at the same time as the cleaning work. , to lose weight; then subtract the number of times in the weight loss of the actual sample, to obtain a more realistic sample weight loss.
(3) Electrochemical method. The appropriate anode and electrolyte are selected, and the sample is an electrolytic method in which a cathode is applied with a direct current. When electrolysis, the cathode generates hydrogen gas, and under the mechanical action of hydrogen bubbles, the corrosion product is peeled off, and the residual loose material can be washed away by mechanical means. The effect of this method is better, and the weight loss of the blank sample is small. An electrolytic operating condition suitable for many metallic materials.
The above is an introduction to the test method of corrosion coupon . I hope everyone can understand the test methods of corrosion coupon and it will be helpful to everyone.
