Effect of Fe, Ni and Cr on the corrosion behaviour of hypereutectic Al-Si automotive alloy in 3.5% NaCl solution at different temperature and velocity

Abstract

The main focus of this study is to examine and evaluate the effect of Fe, Ni and Cr on the corrosion behaviour of hypereutectic Al-Si automotive alloy in 3.5% NaCl solution. Experimental information are attained using conventional gravimetric measurements under different solution temperature and velocity and complemented by resistivity, optical micrograph, scanning electron microscopy (SEM) and X-ray analyzer (EDX) investigations. All the alloys show the negative corrosion rate due to formation of a very thin film of aluminum oxide and hydroxid on the surface. Intermetallic particles in the alloys play a major role in passivity.
 Temperature accelerates the corrosion and the higher velocity breakdown of the passive film. It also affects the resistivity of the alloys. The results from this study also indicate that the temperature and velocity increase the negative corrosion rate of the alloys due to higher rate of chemical reactions. SEM and EDX analysis indicate that the surfaces compose with a thin layer of aluminum oxide and hydroxide corrosion products.

Corrosion Resistance of Fe-Contaminated Al-Si-CU-Zn Alloys Modified With NI and Co and with Variable Secondary Dendrite Arm Spacing

“…As also observed by Kaiser et al [9], the white products were identified as being "mushroom-type" layers. The active dissolution of the alloy resulted in Al(OH)3, which is insoluble in water, and precipitates as a white gel with gelatinous flake aspect [35].…”

“…In other words, the corrosive rate was indeed significantly lower for the alloy with Ni, as assessed after 30-day exposure. In their immersion tests, Kaiser et al [9] observed an inversion of the behavior of the Al alloy containing Ni. While the alloy containing Ni had a greater corrosion rate for shorter periods (1 to 3 days), it demonstrated a lower corrosion rate for longer elapsed times.…”

“…Al and its alloys exposed to aggressive environments, especially those containing chloride ions (Cl -), are sensitive to pitting corrosion [8]. The effects of adding Ni to Al-Si alloys immersed in NaCl solution have been evaluated in some previous studies [9][10][11][12][13]. Hypereutectic Al-Si-Fe-Cu-Zn alloys containing either Ni or Ni/Cr were evaluated and compared through weight loss experiments in 3.5 wt.% NaCl electrolyte [9].…”

“…The effects of adding Ni to Al-Si alloys immersed in NaCl solution have been evaluated in some previous studies [9][10][11][12][13]. Hypereutectic Al-Si-Fe-Cu-Zn alloys containing either Ni or Ni/Cr were evaluated and compared through weight loss experiments in 3.5 wt.% NaCl electrolyte [9]. A higher thickness loss values within the first three days of exposure were associated to the Nicontaining alloy..…”

Results of Sn/Pb solder affected aluminum under wear study

“…The reason behind this increase in wear rate is due to the corrosive attack, next formation of passive films on the surface of the sample which acts as a barrier against further corrosion hence the wear rate is low. After some time, the wear rate increases due to the gradual breakdown of the progressively thicker passive films [34].…”