If the zinc coating is good, but when the light comes out in 3% nitric acid, there is a dark shadow on the coating, and the film is brown when passivation occurs, which may be caused by foreign metal impurities such as copper or lead in the galvanized liquid. When there is a problem in the process of galvanizing, check the temperature and current density first, and then measure and adjust the content of zinc and sodium hydroxide in the bath through the analysis of the bath. Whether DPE levels are low can be determined by Hull cell test.

On the highway, the barbed wire protective net is generally used to prevent people and animals from crossing the highway at will, so as not to interfere with driving and reduce accidents, as well as effectively prevent illegal occupation of highway land and other issues of traffic safety facilities. There are many forms of barbed wire protective nets, commonly used are metal, woven nets, barbed wire and evergreen green gracilaria. In the densely populated areas set up metal woven net, people and animals are less sparse areas of the form of barbed wire, in the toll station, service area and other sections of the structure of hedge and barbed wire. In the past two years, considering the aesthetic problem, some highways in the Pearl River Delta region adopted the fruit plastic spot welding mesh (usually said guardrail mesh), the barbed wire protective mesh is more beautiful, but also durable, the overall effect is good, but the construction requirements are higher, more expensive. General sections should not be used, in the city center, scenic spots or strong requirements for beauty of the section available.