1. The general corrosion characteristics of brass brass brass is a cu-Zn alloy with Zn as the main alloying element, which is called brass because of its yellow color. Brass can be divided into three kinds: single-phase brass, multi-phase brass and special brass. When the zinc content is less than 36% , the single-phase solid solution is formed, so the single-phase brass is also called brass. When the zinc content is 36%-45% , it becomes + duplex brass. When the content of zinc is more than 45% , there are too many phases and the Brittleness is big, so it has no practical value. On the basis of Cu-Zn, SN, MN, AL, FE, Ni, SI and Pb are added to the special brass. Brass corrodes slowly in atmosphere, and corrodes slowly in pure fresh water (0.0025-0.025 MM/YEAR) , corrodes slightly faster in seawater (0.0075-0.1 mm/year) . Fluoride in water has little influence on the corrosion of brass, chloride has more influence, and iodide has more serious influence. In water containing o 2, Co 2, H 2s, so 2, Nh 3 and other gases, the corrosion rate of brass increases dramatically. It is easy to corrode in ore water, especially in water containing fe 2(so 4)3. The corrosion is serious in nitric acid and hydrochloric acid, slow in sulfuric acid and resistant in NaOH solution. The impact corrosion resistance of brass is better than that of pure copper. The corrosion resistance of special brass is better than that of common brass. Adding about 1% Sn into brass can reduce the dezincification corrosion of brass and improve the corrosion resistance in seawater, and adding about 2% pb into brass can increase the wear resistance, so the corrosion rate in flowing seawater is greatly reduced. In order to prevent dezincification corrosion, a small amount of As, SB and P (0.02% ~ 0.05%) can be added, and naval brass containing 0.5% ~ 1.0% MN can improve the strength and have good corrosion resistance. In brass containing 65% cu and 55% cu, part of Zn is replaced by 12%-18% NI. The alloy has excellent corrosion resistance in salt, Alkali and non-oxidizing acid. At the same time, there is no dezincification because of a large amount of NI instead of 2N. In addition to the above corrosion characteristics of brass, there are two important corrosion forms, namely dezincification corrosion and stress corrosion.

2. The factors that influence the stress corrosion cracking of brass are corrosion medium, stress, alloy composition and structure. Corrosion cracking of an alloy occurs only under certain conditions of medium and stress. 

(1) brass with tensile stress in corrosive medium can produce stress corrosion in all media containing ammonia (or NH4 +) , atmosphere, seawater, fresh water, high temperature and high pressure water, and Water Vapor. For example, brass shell cracking (also known as Season cracking) during the summer rainy season is a typical example of brass stress corrosion cracking. In addition, the stress corrosion cracking of brass can be divided into intercrystalline and transcrystalline forms, which mainly occur in film-forming solution and in non-film-forming solution. The mechanism of stress corrosion cracking (SCC) of brass is generally considered as follows: In the film forming solution, a layer of cuprous oxide (cuprous oxide) film with poor toughness is formed on the surface of brass, after embrittlement, the crack extends to the base metal and stops due to slippage. The crack tip is exposed to corrosion solution, and then intergranular permeation, film formation, embrittlement and crack propagation occur. This process is repeated, finally, a step-like discontinuous fracture is formed. In non-film forming solution, stress causes outcrop dislocations on brass surface to dissolve preferentially, leading to crack propagation and fracture along the path of highest dislocation density. In the brass with low zinc content, the dislocation is mainly cellular and the grain boundary is the maximum dislocation density zone, so the intercrystalline fracture occurs. In brass with high zinc content, the dislocation is mainly Planar, stacking fault is the maximum dislocation density zone, so the transgranular fracture occurs. In addition, the crack growth rate will increase with the increase of zinc content because of the stress-induced segregation of zinc atoms at the dislocations and the increased activity of the dislocations. The results show that the industrial atmosphere is the most likely to cause stress corrosion cracking of brass, and the fracture life is the shortest, the rural atmosphere is the second, and the marine atmosphere is the least. This difference in the atmospheric environ