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1 Introduction
Copper-based alloys are among the most important commercial metals due to their excellent electrical and thermal conductivities, good corrosion resistance and ease of manufacture. A range of applications have been developed for Cu30Zn alloy (brass) and Cu30Ni alloy (B30) where they are recommended as high reliability and low maintenance materials for pipe work, tube plates, water boxes, flanges and pump casings in circulating systems such as condensers, heat exchangers and desalination plants. However, they are susceptible to different forms of corrosion such as pitting induced by chloride. One of the most important methods in corrosion protection is to use inhibitors ([6] Modestov et al. , 1994; [18] Zhou et al. , 1997; [14] Xu et al. , 2003; [15] Xu and Zhou, 2003). Few inhibitors for brass and Cu-Ni alloy corrosion have been studied ([2] Alhajji and Reda, 1994; [8] Goncalves et al. , 2002; [7] Allam et al. , 2005; [1] Asan et al. , 2005). Inhibitors should be of low toxicity and easily biodegradable in order to meet environmental protection requirements. Tungstate is an environmentally friendly inhibitor and has been extensively studied for its application in the protection of iron, zinc and aluminium substrates in neutral, acidic and alkaline solutions ([3] Kadher et al. , 1988). Normally it is not feasible to use tungstate alone as a corrosion inhibitor due to its low inhibition ability at low concentrations of tungstate. In most cases, the combination of tungstate with one or more co-inhibitors was described in the literature ([16], [14] Xu et al. , 2001, 2003; [15] Xu and Zhou, 2003; [11] Shibli and Saji, 2005). However, previous literature has not reported the use of tungstate as a corrosion inhibitor for brass and B30.
Polyaspartic acid (PASP) is a type of green water treatment chemical, which is environmentally benign and has good scale inhibiting properties ([5] Low and Koskan, 1993; [9] Robert and Kim, 1997; [10] Roweton and Huang, 1997). Recently most studies of PASP have been focused on the preparation and application of scale inhibitor and only a few on its application as a corrosion inhibitor ([12] Silverman, 1995). The application of PASP as an inhibitor for brass and B30 corrosion has not been reported.
This paper investigated the corrosion inhibition...