Data on the corrosion resistance as-received, annealed and quenched 1060 aluminum alloy in dilute H2SO4 and HCl acid concentrations

The effect of annealing and quenching heat treatment processes on the corrosion resistance of 1060 aluminum alloy was studied by weight loss method in 0.5, 1, 1.5 and 2M H2SO4 and HCl acid media. Alteration of the microstructural constituents of the alloy significantly influenced its corrosion resistance. Data obtained confirmed that quenched aluminum depicted the highest corrosion resistance with highest corrosion rate value of 0.00149 mm/y and 0.02151 mm/y from 2 M H2SO4 and HCl solution. Annealed aluminum exhibited the lowest corrosion resistance with optimal corrosion rates of 0.00768 mm/y and 0.02792 mm/y. Corrosion resistance of as-received aluminum was observed to be intermediate between the values obtained for quenched and annealed aluminum alloy. Annealed AL1060 exhibited the highest standard deviation value in H2SO4 while quenched AL1060 exhibited the highest values in HCl solution. Mean values generally increased with increase in acid solution for the as-received, annealed and quenched AL1060. Statistical data from analysis of variance (ANOVA) shows acid concentration is the statistically relevance sources of variation influence the the corrosion behaviour of as-received, annealed and quenched AL1060 in H2SO4 and HCl solution. The statistical relevance values for acid concentration obtained in H2SO4 solution 83.40%, 97.04% and 89.29% while the corresponding values in HCl solution are 97.94%, 99.29% and 96.07%. The values for exposure time were calculated to be statistically irrelevant in both acids.


INTRODUCTION
Aluminium is an important structural engineering alloy whose application is only behind ferrous alloys as a result of their light weight, relatively high strength and excellent corrosion resistance properties. Their corrosion resistance is due to the initiation and growth of inert, impenetrable protective oxide layer on their surface. The application and production of aluminium has exponential increase in recent years with extensive application as the material of construction for heat exchangers, electrical wires, automotive radiators, aircraft parts, marine components, consumer devices, sports equipment etc. [1][2][3]. Heat treatment is indispensible in the final fabrication and production of aluminium to meet specific property requirements [4][5][6].Aluminium alloys are highly reactive metals and vulnerable to corrosion due to its amphoteric nature wherewith it can sometimes undergo accelerated degradation in the presence of threshold concentrations of salts, acids or bases. Alteration of their metallurgical and microstructure properties in high temperature applications significantly influences their corrosion resistance [7,8]. Several factors are responsible for the corrosion resistance properties of aluminum alloys in aqueous environments such as surface properties of the material, the nature, the temperature, pH and the composition of the electrolyte [9][10][11]. Previous research has shown that corrosion resistance of aluminum is strongly by the heat treatment [12][13][14]. This research focuses on the effect of annealing and quenching heat treatment processes on the corrosion resistance of 1060 aluminium alloy in dilute concentrations of H 2 SO 4 and HCl acid solution.

MATERIAL AND METHODS
As-received 1060 aluminum alloy (AL1060) rod with average length and diameter of 10 mm x 12 mm was machined into three sets of four 4 test specimens with HSS parting tool on a lathe machine. The Al1060 samples were metallographically prepared using emery papers of 80, 120, 220, 800 and 1000 grits. One set of four Al1060 samples were heat treated by annealing in a muffle furnace above the transformation range to 425 o C before slowly cooled to 260 o C and then gradually to room temperature. Another set of four Al1060 samples were heat treated by quenching at a temperature of 425ᴼC in the muffle furnace after which the samples are removed and immediately quenched in distilled water. 0.5M, 1M, W is the weight loss in grams, D is the density in g/cm 2 , A is the area in cm 2 , and T is the time of exposure in hours. W was calculated from the difference between the initial weight of AL1060 (kept constant for 480 h) and every final weight taken at 24 h interval for a total of 480 h.

Coupon measurement
Data for corrosion rate of as-received, annealed and quenched AL1060 from H 2 SO 4 and HCl solutions are presented from Tables 1-3. AL1060 corroded progressively with increase in concentration of both acids. AL1060 is an amphoteric metal, as a result changes in the surface characteristics of the alloy causes spontaneous reaction which implies breakdown of the protective oxide. The protective oxide in AL1060 had limited effect in the presence of higher concentrations of H 2 SO 4 and HCl. Generally, the corrosion rate values for as-received, annealed and quenched AL1060 in HCl are relatively higher than the values obtained in H 2 SO 4 due to the higher reactivity and smaller size of Clions. Annealed AL1060 specimens showed higher susceptibility to corrosion than the as-received specimens from observation of its corrosion rate values which are higher, while quenched Al 1060 showed the highest corrosion resistance compared to the as-received and annealed AL1060 due to its lower corrosion rate values. The influence of exposure time on 1060AL is quite varied as in some cases the corrosion rate decreased and vice versa.

Statistical data
The mean and standard deviation for as-received, annealed and quenched AL1060 from H 2 SO 4 and HCl solution are shown in   Tables 5 and 6. The statistical relevance is the percentage significance of each source of variation relevance to the corrosion rate output. The mean square ratio is the calculated significance factor which must be greater than the theoretical significance factor (threshold factor) the statistical relevance value to be acceptable. The statistical relevance value in Table 5 shows H 2 SO 4 concentration is the only statistically relevant source of variation important in the resulting corrosion rate output for asreceived, annealed and quenched AL1060 with values of 83.40%, 97.04% and 89.29%. The corresponding values for exposure time are generally below 5%. However, the value of mean square ratio for the heat treated and as-received AL1060 are lower than the theoretical significance factor which showsexposure time is statistical irrelevant in the corrosion value output of the alloy. The results obtained for as-received, annealed and quenched AL1060 in HCl solution shown in Table 6 is generally similar to the values obtained in Table 5

CONCLUSION
Data obtained from electrochemical corrosion behaviour of as-received, quenched and annealed 1060 aluminium alloy showed that the quenched alloy generally had the highest corrosion resistance. The as-received aluminium specimens exhibited a lower corrosion resistance than the quenched specimens though the corrosion rates from HCl solution are generally higher than values obtained from H 2 SO 4 . Annealed aluminium alloy had the highest corrosion rate.The standard deviation values for the heat treated and as-received alloy increased with acid concentration while the standard deviation values for HCl solution were generally higher than the values in H 2 SO 4 solution with respect to exposure time.Statistical data from ANOVA acid concentration is the dominant source of variation statistically relevant for the resulting corrosion rate value with respect to exposure time for the heat treated and asreceived Al alloy

ACKNOWLEDGEMENT
The author is grateful to Covenant University Ota, Ogun State, Nigeria for the sponsorship and provision of research facilities for this project.