A sacrificial anode for cathodic protection

Abstract

The present disclosure provides a sacrificial anode for cathodic protection comprising Zinc, and Aluminium directly recovered from a galvalume dross. A method for preparing a sacrificial anode for cathodic protection is also provided.

Description

[0001] “A SACRIFICIAL ANODE FOR CATHODIC PROTECTION”

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to sacrificial anodes. More particularly, the present disclosure relates to sacrificial anodes comprising zinc and aluminium obtained from galvalume dross. The present disclosure also provides a method for preparing said sacrificial anode.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] Steel is the most widely used metal worldwide. The per capita consumption of steel is an indicator of the development and modernization of any country. Corrosion of steel is a serious concern when subjected to various environmental conditions. Galvanized steels such as commercial steel, deep drawing steel, structural steel, HSLA steel, and forming steel have been most popular due to three factors: galvanized steels have approximately twenty times more corrosion resistance than steels, an effective method of sacrificial cathodic protection, and most importantly these coatings are economical. Galvanized coatings show inadequate performance in ambient atmospheric conditions. Hence, extensive research has been conducted to enhance the corrosion resistance of hot-dip galvanized steel. Many alloy combinations have been investigated, such as Zn-Ni, Zn-Co, Zn-Sn, Zn-Al. Zn-Al coating showed the best performance among all other alloy combinations. Zn-Al coated steel is also known as galvalume steel.

[0006] Galvalume -coated steels show better corrosion resistance and longer product life than galvanized steel in atmospheric conditions. Due to the sacrificial nature of zinc, galvalume coatings provide better corrosion resistance, whereas aluminum presence ensures the formation of aluminum oxide under natural environmental conditions. Aluminum oxide acts as a physical barrier and protects the steel from further corrosion; hence, it leads to a longer product life.

[0007] Generally, structural steel and formed steel used for construction are coated with galvalume. Galvalume steel is mostly used for roofing panels, building panels, wall panels, unexposed automotive parts, ductwork, transportation, etc.Galvalume coating on steel is done using the hot-dip process. During the hot-dip galvalume coating of steel, dross forms in the bath. Dross forms due to the solubility of iron in the galvalume bath. Galvalume dross is mostly utilized as a filler in the idols, and scripture-making where rest of the dross is left unutilised. Therefore, there is a significant research gap in identifying the improved sustainable fields of application to encourage the recovery and reuse of galvalume waste, such as galvalume dross.

[0008] Therefore, there is a need to develop a method for employing galvalume dross in an effective simple and cost-effective manner.

[0009] STATEMENT OF THE DISCLOSURE

[0010] The present disclosure relates to a sacrificial anode, comprising zinc and aluminium directly recovered from galvalume dross.

[0011] The present disclosure also relates to a method for preparing the sacrificial anode directly from galvalume dross, comprising:

[0012] a) heating a galvalume dross to a temperature of about 740 to about 780 deg C to obtain a molten zinc and aluminium residue; and

[0013] b) pouring the molten zinc and aluminium residue directly into a mold to cast the sacrificial anode.

[0014] BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

[0015] In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:

[0016] Fig. la is a photograph of an as received galvalume dross as per an embodiment of the invention.Fig. lb is a photograph of a galvalume dross having first composition as per the embodiment of the invention.

[0017] Fig. 1c is a photograph of a galvalume dross having second composition as per the embodiment of the invention.

[0018] Figs. 2a & 2b shows electrochemical behaviour test arrangement, and anode service life test setup respectively, as per the embodiment of the invention.

[0019] Figs. 3(a & c) shows Bright-field optical micrograph, Figs. 3(b & d) Dark-field optical micrograph, Figs. 3(e & g) SEM micrograph, Figs.3(f & h) EDS elemental mapping, Figs. 3(i & j) EDS elemental composition in wt% of an anode sample of the galvalume dross having first composition and an anode sample of the galvalume dross having second composition, respectively, and Fig 3(k) shows XRD pattern of the anode sample of the galvalume dross having second composition and the anode sample of the galvalume dross having first composition as per the embodiment of the invention.

[0020] Figs. 4a-4h shows electrochemical behaviour of the anode sample of the galvalume dross having first composition and the anode sample of galvalume dross having second composition for Open circuit potential variation with time, linear polarization plot, Potentiodynamic polarization, Nyquist plot, Bode magnitude plot, Bode phase plot, and EIS electrical circuit for the anode sample of galvalume dross having first composition and EIS Electrical circuit for anode sample of galvalume dross having second composition in 3.5 wt% NaCl solution respectively as per the embodiment of the invention.

[0021] Figs. 5a, 5c, 5e shows SEM micrograph, EDS elemental mapping, Elemental composition of the anode sample of galvalume dross having first composition respectively, and Figs. 5b, 5d, 5f shows SEM micrograph, EDS elemental mapping, Elemental composition of the anode sample of galvalume dross having second composition after potentiodynamic test in 3.5 wt% Nacl environment, respectively, as per the embodiment of the invention.

[0022] Fig 6. shows schematic of various sacrificial anodes showing the range of anode capacity along with the reference anode efficiency as per the embodiment of the invention.

[0023] Fig 7a- 7b shows Raman spectra after PD test and Raman spectra after service life test respectively for the anode sample of galvalume dross having first composition and the second composition.Figs 7c-7e shows after performance test and after post anode performance test cleaning for the anodes made of the dross having first composition and Figs 7d-7f shows after performance test and after post anode performance test cleaning for the anodes made of the dross having second composition as per the embodiment of the invention.

[0024] DETAILED DESCRIPTION OF THE DISCLOSURE

[0025] The present disclosure provides a sacrificial anode and a method for preparing the same from zinc dross.

[0026] With respect to the use of substantially any plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations may be expressly set forth herein for sake of clarity. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” or “containing” or “has” or “having”, or “including but not limited to” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0027] Reference throughout this specification to “some embodiments”, “one embodiment”, “an embodiment”, “some exemplary embodiments”, “some preferred embodiments”, or “some non-limiting embodiments” means that a particular feature, structure or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in some embodiments”, “in one embodiment”, “in an embodiment”, “in some exemplary embodiments”, “in some preferred embodiments”, or “in some non-limiting embodiments”, in various places throughout this specification may not necessarily all refer to the same embodiment. It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.The term “about” as used herein encompasses variations of + / -5% and more preferably + / -2.5%, as such variations are appropriate for practicing the present invention.

[0028] During the hot-dip galvalume coating of steel, dross forms in the bath. Dross forms due to the solubility of iron in the galvalume bath. Galvalume dross is mostly utilized as a filler in the idols, and scripture-making where rest of the dross is left unutilised. Therefore, there is a significant research gap in identifying the improved sustainable fields of application to encourage the recovery and reuse of galvalume waste, such as galvalume dross.

[0029] Accordingly, the present disclosure provides a sacrificial anode for cathodic protection, comprising zinc, aluminium directly recovered from a galvalume dross. The sacrificial anode of the present disclosure is economical and at the same time exhibits satisfactory performance in providing sacrificial protection to steel substrates. The sacrificial anode also helps in utilizing the unutilised galvalume dross.

[0030] In some embodiments, the galvalume dross includes a galvalume dross having first composition or a galvalume dross having second composition. _In some embodiments, the galvalume dross having first composition, comprises about 56.2 + 2 wt% aluminium (Al), including values and ranges therebetween, Zinc (Zn) about 31.6 + 2 wt%, including values and ranges therebetween, Iron (Fe) about 5.2 + 2 wt% including values and ranges therebetween, Silicon (Si) about 3.3 + 1 wt% including values and ranges therebetween, and rest non-traceable elements along with oxides including values and ranges therebetween.

[0031] For example, the galvalume dross having first composition of the present disclosure comprises about 54.2 wt%, about 55.2 wt%, about 56.2 wt%, about 57.2 wt%, or about 58.2 wt% aluminium (Al), including values and ranges therebetween, about 29.6 wt%, about 30.6 wt%, about 31.6 wt%. about 32.6 wt%, about 33.6 wt% Zinc (Zn), including values and ranges therebetween, about 3.2 wt%, about 4.2 wt%, about 5.2 wt%, about 6.2 wt%, about 7.2 wt% Iron (Fe) including values and ranges therebetween, about 2.3 wt%, about 3.3 wt%, about 4.3 Silicon (Si) wt% including values and ranges therebetween, and rest non-traceable elements along with oxides including values and ranges therebetween.

[0032] In some embodiment the galvalume dross and the galvalume dross having first composition have same composition.In some embodiments, the galvalume dross having second composition, comprises: about 51.5 + 2 wt% aluminium (Al), including values and ranges therebetween, about 38.9 + 2 wt% Zinc (Zn), including values and ranges therebetween, Iron about 1.5 + 0.5 wt%, including values and ranges therebetween, about 4.9 + 1 wt% Silicon (Si), including values and ranges therebetween, and rest non-traceable elements along with oxides including values and ranges therebetween.

[0033] For example, the galvalume dross having second composition, comprises: about 49.5, about 50.5, about 51.5, about 52.5, about 53.5 wt% aluminium (Al), including values and ranges therebetween, about 36.9, about 37.9, about 38.9, about 40.9 Zinc (Zn) wt%, including values and ranges therebetween, Iron (Fe) about 1.0, about 1.1, about 1.2 about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0 wt%, including values and ranges therebetween, about 3.9, about 4.9, about 5.9 Silicon (Si) wt%, including values and ranges therebetween, and rest non-traceable elements along with oxides including values and ranges therebetween.

[0034] In some embodiment, the sacrificial anode for cathodic protection made through the galvalume dross having first composition exhibits open circuit potential (OCP) about -1.10 V + 0.02V (with respect to saturated calomel electrode) including values and ranges therebetween. For example the sacrificial anode for cathodic protection made through the galvalume dross having first composition exhibits open circuit potential (OCP) about -1.12V, about -1.11V, about -1.10V, about -1.09V, about -1.08V, (with respect to saturated calomel electrode) including values and ranges therebetween.

[0035] In another embodiment, the sacrificial anode for cathodic protection made through the galvalume dross having second composition exhibits open circuit potential (OCP) about -1.03 + 0.02 V (with respect to saturated calomel electrode) including values and ranges therebetween. For example, the sacrificial anode for cathodic protection made through the galvalume dross having second composition exhibits open circuit potential (OCP) about -1.05 V, about -1.04 V, about -1.03 V, about -1.02 V, about -1.01 V (with respect to saturated calomel electrode) including values and ranges therebetween.In some embodiment the sacrificial anode made the through the galvalume dross having first composition exhibits closed circuit potential (CCP) being about -0.97 + 0.05 V as per DNV-RPB401, 2010 standard including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having first composition exhibits closed circuit potential (CCP) being about -1.02V, about -1.01V, about -1.00V, about -0.99V, about -0.98V, about -0.97V, about -0.96V, about -0.95V, about -0.94V, about -0.93V, about -0.92V as per DNV-RPB401, 2010 standard including values and ranges therebetween.

[0036] In some embodiment the sacrificial anode made the through the galvalume dross having second composition exhibits closed circuit potential (CCP) being about -0.868 + 0.05 V as per DNV-RPB401, 2010 standard including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having second composition exhibits closed circuit potential (CCP) being about -0.873V, about -0.872V, about -0.871V, about -0.870V, about -0.869V, about -0.868V, about -0.867V, about -0.866V, about -0.865 V as per DNV-RPB401, 2010 standard including values and ranges therebetween.

[0037] In some embodiment, the sacrificial anode made the through galvalume dross having first composition exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1550.20 + 5 including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having first composition exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1545.2, about 1546.2, about 1547.2, about 1548.2, about 1549.2, about 1550.2, about 1551.2, about 1552.2, about 1553.2, about 1554.2, about 1555.2 including values and ranges therebetween.

[0038] In some embodiment, the sacrificial anode made the through galvalume dross having second composition exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1458.82 ± 10 including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having second composition exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1448.82, about 1550.82, about 1453.82, about 1454.82, about 1455.82, about 1456.82, about 1457.82, about 1458.82, about 1459.82, about 1460.82, about 1461.82, about 1462.82, about 1463.82, about 1465.82, about 1468.82 including values and ranges therebetween.

[0039] In some embodiment, the sacrificial anode made through the galvalume dross having first composition exhibits Experimental anode capacity (Qexp, Ah / kg) of about 2255 + 5 including values and ranges therebetween. For example, the sacrificial anode made through galvalumedross having first composition exhibits Experimental anode capacity (Qexp, Ah / kg) of about 2250, about 2251, about 2252, about 2253, about 2254, about 2255, about 2256, about 2257, about 2258, about 2259, about 2260 including values and ranges therebetween.

[0040] In some embodiment, the sacrificial anode made through the galvalume dross having second composition exhibits Experimental anode capacity (Qexp, Ah / kg) of about 860 ± 10 including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having second composition exhibits Experimental anode capacity (Qexp, Ah / kg) of about 850, about 852, about 855, about 856, about 857, about 858, about 859, about 860, about 861, about 862, about 863, about 864, about 865, about 867, about 870 including values and ranges therebetween.

[0041] In some embodiment, the sacrificial anode made through the galvalume dross having first composition exhibits Consumption rate (kg / AY) about 3.88 + 0.2 including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having first composition exhibits Consumption rate (kg / AY) about 3.68, about 3.72, about 3.76, about 3.80, about 3.84, about 3.88, about 3.92, about 3.96, about 4.00, about 4.04, about 4.08 including values and ranges therebetween.

[0042] In some embodiment, the sacrificial anode made through the galvalume dross having second composition exhibits Consumption rate (kg / AY) about 10.18 ± 0.2 including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having second composition exhibits Consumption rate (kg / AY) about 9.98, about 10.08, about 10.18, about 10.28, about 10.38 including values and ranges therebetween.

[0043] In some embodiment, the sacrificial anode made the through galvalume dross having second composition exhibits Anode efficiency of about 58.95 + 5% including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having second composition exhibits Anode efficiency of about 53.95%, about 54.95%, about 55.95%, about 56.95%, about 57.95%, about 58.95%, about 59.95%, about 60.95%, about 61.95%, about 62.95%, about 63.95 % including values and ranges therebetween.

[0044] In some embodiment, the sacrificial anode made through the galvalume dross having first composition exhibits Reference anode efficiency of about 85.06 + 5% (with reference to pure Al anode) including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having first composition exhibits Reference anode efficiency of about 80.06%, about 81.06%, about 82.06%, about 83.06%, about 84.06%, about 85.06%, about86.06%, about 87.06%, about 88.06%, about 89.06%, about 90.06 % (with reference to pure Al anode) including values and ranges therebetween.

[0045] In some embodiment, the sacrificial anode made through the galvalume dross having second composition exhibits Reference anode efficiency of about 32.44 + 5% (with reference to pure Al anode) including values and ranges therebetween. For example, the sacrificial anode made through galvalume dross having second composition exhibits Reference anode efficiency of about 27.44%, about 28.44%, about 29.44%, about 30.44%, about 31.44%, about 32.44%, about 33.44%, about 34.44%, about 35.44%, about 36.44%, about 37.44% (all with reference to pure Al anode) including values and ranges therebetween.

[0046] The present invention also provides a method for preparing a sacrificial anode for cathodic protection, is described. The method comprises

[0047] heating a galvalume dross to a temperature of about 740 to about 780 deg C to obtain a molten zinc and aluminium residue; and

[0048] pouring the molten zinc and aluminium residue directly into a mold to cast the sacrificial anode.

[0049] The present method of preparing the sacrificial anode from the galvalume dross is a single step method which does not involve other complex steps such as super gravity separation.

[0050] In some embodiments, the galvalume dross is heated to a temperature of about 740-780°C, about

[0051] 740-760°C, about 740-765°C, about 740-770°C, about 740-775°C, about 740-780°C, about 745-750°C, about 745-755°C, about 745-760°C, about 745-765°C, about 745-770°C, about 745-775°C, about 745-780°C, about 750-755°C, about 750-760°C, about 750-765°C, about 750-770°C, about 750-775°C, about 750-780°C, about 755-760°C, about 755-765°C, about 755-770°C, about 755-775°C, about 755-780°C, about 760-765°C, about 760-765°C, about 760-770°C, about 760-775°C, about 760-780°C, about 765-770°C, about 765-775°C, about 765-780°C, about 770-775°C, about 770-780°C, about 775-780°C, about 740°C, about 741°C, about 742°C, about 743°C, about 744°C, about 745°C, about 746°C, about 747°C, about 748°C, about 749°C, about 750°C, about 751°C, about 752°C, about 753°C, about 754°C, about 755°C, about 756°C, about 757°C, about 758°C, about 759°C, about 760°C, 761°C, about 762°C, about 763°C, about 764°C, about 765°C, about 766°C, about 767°C, about 768°C, about 769°C, about 770°C, about 771 °C, about 772°C, about 773°C, about 774°C,about 775°C, about 776°C, about 778°C, about 779°C, about 780°C including values and ranges therebetween.

[0052] In some embodiments, the galvalume dross is heated to a temperature of about 745 deg C. In some embodiment, the galvalume dross is heated for about 15mins to about 20 mins, about 15-19 mins, about 15-18 mins, about 15-17 mins, about 15-16 mins.

[0053] In some embodiment, the galvalume dross is heated in a furnace.

[0054] In some embodiment, the sacrificial anode made through the method mentioned above exhibits open circuit potential (OCP) being -1.03 ± 0.02V (with respect to saturated calomel electrode) including values and ranges therebetween.

[0055] In some embodiment, the sacrificial anode made through the method mentioned above exhibits closed circuit potential (CCP) being about -0.868 + 0.05 as per DNV-RPB401, 2010 standard including values and ranges therebetween.

[0056] In some embodiment, the sacrificial anode made through the method mentioned above exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1458.82 ± 10 including values and ranges therebetween.

[0057] In some embodiment, the sacrificial anode made through the method mentioned above exhibits Experimental anode capacity (Qexp, Ah / kg) of about 860 ± 10 including values and ranges therebetween.

[0058] In some embodiment, the sacrificial anode made through the method mentioned above exhibits Consumption rate (kg / AY) about 10.18 ±0.2 including values and ranges therebetween. In some embodiment, the sacrificial anode made through the method mentioned above exhibits Anode efficiency of about 58.95 ± 5 (%) including values and ranges therebetween.

[0059] In some embodiment, the sacrificial anode made through the method mentioned above exhibits reference anode efficiency of about 32.44 ± 5 % (with reference to pure Al anode) including values and ranges therebetween.

[0060] In some embodiment, the galvalume dross used in the method mentioned above comprises Aluminium (Al) about 56.2 + 2 including values and ranges therebetween, Zinc (Zn) about 31.6 + 2 including values and ranges therebetween, Iron (Fe) about 5.2 + 2 including values and ranges therebetween, Silicon (Si) 3.3 + 1 including values and ranges therebetween and rest non-traceable elements along with oxides including values and ranges therebetween.In some embodiment the galvalume dross includes a galvalume dross having second composition comprising, Aluminium (Al) about 51.5 + 2 including values and ranges therebetween, Zinc (Zn) about 38.9 + 2 including values and ranges therebetween, Iron (Fe) about 1.5 + 0.5 including values and ranges therebetween, Silicon (Si) about 4.9 + 1 including values and ranges therebetween and rest non traceable elements along with oxides including values and ranges therebetween.

[0061] In some embodiment, a sacrificial anode for cathodic protection, comprises Zinc, aluminium directly recovered from a galvalume dross having a first composition comprising Aluminium (Al) about 56.2 + 2 including values and ranges therebetween, Zinc (Zn) about 31.6 + 2 including values and ranges therebetween, Iron (Fe) about 5.2 + 2 including values and ranges therebetween, Silicon (Si) 3.3 + 1 including values and ranges therebetween and rest non-traceable elements along with oxides including values and ranges therebetween.

[0062] In some embodiment a sacrificial anode for cathodic protection, comprises Zinc, aluminium directly recovered from a galvalume dross having second composition comprising Aluminium (Al) about 51.5 + 2 including values and ranges therebetween, Zinc (Zn) about 38.9 + 2 including values and ranges therebetween, Iron (Fe) about 1.5 + 0.5 including values and ranges therebetween, Silicon (Si) about 4.9 + 1 including values and ranges therebetween and rest non traceable elements along with oxides including values and ranges therebetween.

[0063] In some embodiments, the sacrificial anode prepared by the method of the present disclosure exhibits properties such as open circuit potential (OCP), closed circuit potential (CCP), theoretical anode capacity Experimental anode capacity Consumption rate Anode efficiency reference anode efficiency as described in the embodiments above for the sacrificial anode. Each of those embodiments are not being reiterated herein for the sake of brevity but fall wholly within the scope of the method of the present disclosure.

[0064] The present method of preparing the sacrificial anode from Galvalume dross is a single step method which does not involve separate purification of zinc or other complex steps such as super gravity separation.

[0065] In some embodiments, the Galvalume dross is heated in a furnace such as muffle furnace, resistance heating furnace, gas fired furnace.

[0066] It is to be understood that the foregoing descriptive matter is illustrative of the disclosure and not a limitation. While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that manychanges can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Similarly, additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein.

[0067] Descriptions of well-known / conventional methods / steps and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above-described embodiments, and in order to illustrate the embodiments of the present disclosure certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the following examples should not be construed as limiting the scope of the embodiments herein.

[0068] Experimental procedure

[0069] 1.1 Sample preparation

[0070] Anode made up of Galvalume dross having first composition hereinafter as “first galvalume anode”. The as received galvalume dross were received, as shown in Fig 1(a). The as received galvalume dross were machined to get the anodes of 1.27 cm in diameter and 157 cm in length by using a wire electric discharge machine (EDM) to produce a galvalume dross, as shown in Fig 1(b). The average weight of the first galvalume anode was approximately 48 grams. The first as-received galvalume blocks were porous, as observed in Fig 1(b).

[0071] Anode made up of Galvalume dross having second composition, hereinafter referred as "second galvalume anode”). For making the second galvalume dross, the as received galvalume dross shown in Fig. 1(a) were cut down into small blocks so these blocks could fit into the crucible. The crucible was placed into the muffle furnace set to heat the galvalume dross at 745 °C for 15-20 min to refine the as received galvalume dross. The liquid metal was covered witha thin layer of dross, which was broken by a gentle punch with a steel rod. Subsequently, the molten metal was poured into the permanent molds to cast the anodes. The cast anodes were machined on a lathe to get the anodes of 1.57 cm in diameter and 157 cm in length. The average weight of anode samples of second galvalume dross was approximately 100 g. The casting yield of this process was approximately 62 %. The casting yield is the ratio of recovered galvalume material to the galvalume dross fed to the crucible.

[0072] All the first and second galvalume dross anode samples obtained from first and second routes were then cleaned in a solution of 10-15 wt% NaOH at 50°C for 15 min. Afterward, the anodes were rinsed in tap water and then dried in hot air. Finally, samples were ultrasonicated in acetone for 10 min. The anode sample of second galvalume dross is shown in Fig 1(c).

[0073] Samples of 5 mm thickness were cut down from the first galvalume dross to perform microstructural characterization and electrochemical investigation. For microstructural characterization, samples were ground up to 2500 silicon carbide abrasive paper in intermittent wet conditions. Afterward, the anode samples of the first galvalume dross and the second galvalume dross were cloth polished by using 0.1 pm alumina particle suspension liquid for 30 min. Anode samples of the first galvalume dross and the second galvalume dross were cleaned in running tap water, dried by hot air, and eventually ultrasonicated in acetone for 5 min. For electrochemical investigations, samples were ground up to 1200 silicon carbide abrasive paper, followed by the sample cleaning process.

[0074] 1.2 Chemical composition and density measurement

[0075] The chemical composition was investigated by using energy dispersive spectroscopy (EDS). Carl Zeiss EVO 50 scanning electron microscopy machine equipped with energy dispersive x-ray (EDX) microanalysis hardware was used at 20 kV. The density of the polished anode of first galvalume dross was measured using the mass and volume of the anodes whereasanode of second galvalume dross samples density was measured by using the Archimedes principle. The porosity of the anode samples of the first galvalume dross samples was measured with the help of Image J software.

[0076] 1.3 Microstructural and phase characterization

[0077] The anode samples of the first galvalume dross and the second galvalume dross postpolishing were etched in Keller’s reagent consisting of 95 ml water, 2.5 ml nitric acid (HNO3), 1.5 ml hydrochloric acid (HC1), and 1.0 ml HF for 10 s, followed by cleaning in warm water. The samples were dried using a hot air blower. The optical microstructures were observed in bright field and dark field mode by using a Leica DM6000 M microsystem. Scanning electron micrograph (SEM) images were also taken at higher magnifications by using a W-SEM (Carl Zeiss EVO 50) at 20 kV. W-SEM is attached with energy-dispersive X-ray (EDX) microanalysis hardware. EDX was performed to investigate the elemental distribution throughout the sample surface. Moreover, SEM was used to analyze the corrosion product morphology formed on the surface of the anode samples of the first galvalume dross and the second galvalume dross after the electrochemical test. Xpert Pro pan analytical diffractometer operated at 40 mA and 40 kV was used to perform the X-ray diffraction (XRD) in the Bragg’s angle range of 10°-90° with a step size of 0.02° at room temperature by using Cu Ka (X = 0.15405 nm) radiation. Raman spectroscopy was performed to investigate the corrosion products formed after the electrochemical and anode performance tests with the help of an Acton Spectropro SP-2500. The corrosion products were excited by a 532 nm wavelength Nd-YAG laser attached to the Olympus optical microscope.

[0078] 1.4 Electrochemical tests

[0079] Electrochemical tests such as open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization (LP), and potentiodynamic polarization (PD) wereperformed in 3.5 wt% NaCl environment on an AMETEK VersaSTAT 3 potentiostat in the respective order. AMETEK VersaSTAT 3 consists of a three -electrode system, as shown in Fig.

[0080] 2(a). The three electrodes are the reference electrode, working electrode, and counter electrode. Saturated calomel electrode (SCE) was used as the reference electrode. The standard reference electrode potential (E°) of SCE is 0.241 V with respect to the standard hydrogen electrode (SHE). A platinum wire was used as a counter electrode. The anode samples of the first galvalume dross and the second galvalume dross were used as working electrodes.

[0081] A round bottom cell was filled with 250 ml 3.5 wt % NaCl solution. All three electrodes were placed properly in the cell. The reference electrode was placed close to the working electrode sample surface for accurate measurement of electrical double-layer (EDL) potential. All the connections were cleaned and connected properly. To achieve the steady state EDL potential in the open system, open circuit potential (OCP) test was performed for 7200 s. Afterward, EIS test was performed with a sinusoidal perturbation of ± 10 mV with respect to OCP and in the frequency range of 10 KHz to 10 mHz. EIS test data were fitted with the help of Zsimpwin software, and the electrical analogy of EDL was studied. Subsequently, linear polarization (LP) test was performed as per ASTM standard G102 - 89 in the potential range of ±20 mV at a scan rate of 0.166 mV / s. Linear polarization indicates the resistance offered by the material against corrosion. Linear polarization can be calculated as:

[0082] RP= (~

[0083] — -corr

[0084] Here, AE and Ai are changes in overpotential (VSCE) and current density (pA / cm2), respectively. Potentiodynamic polarization tests were performed in the range of -0.25 mV with respect to OCP to -0.5 VSCE at a scan rate of 0.166 mV / s. The values of corrosion potential (Ecorr) and corrosion current density (icon) were obtained from the PD test. Corrosion current density data was used to calculate the corrosion rate in mm / y as per Faraday’s law( -3.23 X 103X imrr x FW A.l. Z ~n anod.e

[0085]

[0086] PAl-Zn anode

[0087] where icorr is the corrosion current density (pA / cm2), EWAI-ZII anode and PAI-ZU anode are the equivalent weight (g) and density (g / cm3) of the anode samples of the first galvalume dross and the second galvalume dross, respectively. All the electrochemical tests were carried out three times to check the reproducibility of the data.

[0088] 1.5 Anode performance test

[0089] As per the standard DNV-RP-B401, the performance of a sacrificial anode is determined by the closed-circuit potential (CCP, VSCE), anode capacity (Ah / kg), anode consumption rate (kg / AY), and anode efficiency (%). The test configuration, as shown in Fig.

[0090] 2(b), followed the ASTM G97-97 guidelines. Three steel beakers of 625 ml capacity were used as a cathode. These beakers were level-filled with artificial seawater solution prepared as per the standard ASTM D 1141. The copper coulometer was used to measure the total charge passed in ampere-hours (Ah) during the test. The solution for the copper coulometer was made using 235 g of CuSO4.5H2O, 50 cm3of ethyl alcohol, 27 mb of H2SO4, and 900 ml of DI water. The plates of copper and wire of standard dimensions, as per ASTM G97-97, were cleaned with 180 grit size abrasive paper followed by water cleaning. Afterward, copper plates and wire were ultrasonicated in acetone for 5 min.

[0091] The bottom part of the anode samples of the first galvalume dross and the second galvalume dross were covered with non-conducting Teflon tape. The effective exposed area of the anode samples of the first galvalume dross and anode samples of the second galvalume dross in the artificial seawater solution was 54 cm2and 60 cm2, respectively. The effective area in the case of the anode samples of the first galvalume dross was limited by the dimensions of the block received. The anode performance test was performed separately for the anode samples of the first galvalume dross and the second galvalume dross. A direct current powersource was used to deliver the variable current for 4 days (96 h ± 4 h), as shown in Table 1 below, as per the standard DNV-RP-B401.

[0092] Table 1

[0093] Exposed area Impressed Exposed area Impressed Current

[0094] Test of first current of first of second current of first density

[0095] duration galvalume galvalume anode galvalume galvalume anode (A / cm2)

[0096] anode (cm2) (mA) anode (cm2) (mA)

[0097] Day 1 1.5 54 81 60 90 Day 2 0.4 54 22 60 24 Day 3 4.0 54 216 60 240 Day 4 1.5 54 81 60 90

[0098]

[0099] The closed-circuit potential was measured at the end of each day with the help of a saturated calomel electrode (SCE). After the completion of the test, anodes were removed from the solution and cleaned in a 250 g CrCh solution in 1000 ml DI water. After cleaning, the anodes were washed in running tap water and dried in hot air with the help of a blower. The weight of the anodes was measured. The copper wire was taken out of the coulometer solution and kept in the oven at 120° C temperature for 15 min for drying. The final weight of the copper wire was measured.

[0100] 2. Results and Discussions

[0101] 2.1 Chemical Composition and Density Measurement

[0102] The chemical compositions in wt% of the anode samples of the first galvalume dross and the second galvalume dross are shown in Table 2 below.Table 2

[0103] Non-traceable elements Elements wt. (%) Al Zn Fe Si with oxides

[0104] First galvalume

[0105] 56.2 31.6 5.2 3.7 3.3 anode

[0106] Second galvalume

[0107] 51.5 38.9 1.5 3.2 4.9

[0108]

[0109] anode

[0110] Table 2 shows that the presence of aluminum and iron is higher in the anode samples of the first galvalume dross. During the recovery process of galvalume dross at 745 ° C, the flowability of zinc is higher than aluminum due to its lower melting temperature which is reflected in the form of higher wt% of zinc in the second galvalume anode. The decrease in the content of iron after the recovery process was also observed during the processing of galvanizing dross. Iron predominantly stays in the dross residue after processing. The calculated geometric densities (mass / volume) of the anode samples of first galvalume dross and second galvalume dross are 2.414 g / cm3and 3.74 g / cm3. The density of the anode samples of second galvalume dross is nearly equal to the density of pure galvalume alloy (3.75 g / cm3). The lower density of the anode samples of first galvalume dross in comparison to galvalume alloy is due to low zinc content and porosity. The porosity of the anode samples of first galvalume dross was found to be in the range of 8 to 12%.

[0111] 2.2 Microstructure & phase Characterization

[0112] Al and Zn rich zones in both the anode samples of the first galvalume dross as well as anode samples the second galvalume dross are evident from the bright field and dark field mode optical micrographs in Fig. 3(a and b) and 3(c and d), respectively. However, the zones are much finer in the anode samples the second galvalume dross one. The anode samples of fire first galvalume dross one contains porosity (Fig. 3(e)), and the anode samples of the second galvalume dross are nearly free from porosity (Fig. 3(g)). The finer structure of the second oneis also evident here. The elemental area mapping of the first and second galvalume anodes is shown in Fig. 3(f) and 3(h), respectively. All the elements are also shown in different images. Si and iron are locally enriched in both cases. Other elements are homogeneously present. Al content is higher in the anode samples of the first galvalume dross, whereas it is Zn rich in the second anode of the second galvalume dross. Fe content is less in the second one whereas Si is less in the first anode. The elemental compositions of the first and second galvalume anodes in wt% are shown in Fig. 3(i) and 3(j), respectively. X-ray diffraction (XRD) data were analyzed for the anode samples of the first galvalume dross and the second galvalume dross, as shown in Fig 3(k).

[0113] 2.3 Electrochemical Behavior

[0114] 2.3.1 Open circuit potential (OCP), Linear Polarization (LP), and Potentiodynamic Polarization (PD)

[0115] All the results of electrochemical tests are summarized in Table 3 below.

[0116] OCP, OCP, Rp, kfl Icorr,

[0117] Materials Ecorr, VSCE CR, mm / y VSCE VCSE cm2jiA / cm2

[0118] First

[0119] -1.10 -1.18 0.660 -1.14 10.57 0.141 galvalume

[0120] anode

[0121] Second

[0122] -1.03 -1.11 3.116 -1.02 2.08 0.029 galvalume

[0123]

[0124] anode

[0125] The measured OCPs of the anode samples of the first galvalume dross and the second galvalume dross were -1.10 VSCE and -1.03 VSCE, respectively (Fig. 4(a)). The more active OCP of the anode samples of the first galvalume dross indicates the significantly higher aluminum presence in the form of Al rich phase. The OCP of the anode samples of first galvalume dross is close to the aluminum anode, whereas the OCP of the anode samples second galvalume drosis near the zinc anode. Subsequently, Polarization resistance was measured bylinear polarization (LP) test shown in Fig. 4b. Polarization resistance indicates the resistance offered by the anode samples of first galvalume dross and second galvalume dross against the flow of current. The polarization resistance of the anode samples of first galvalume dross (0.660 kQ cm2) was observed significantly lower than the anode samples of second galvalume dross (3.116 k cm2). This could be due to the active nature of the aluminum present in the anode samples of first galvalume dross. Aluminum is more active in galvanic series as compared to zinc. However, similar results of polarization resistance were also observed during the EIS study. In the end, potentiodynamic polarization (PD) test was performed. It could be understood from the values of OCPs and corrosion potential which fall in nearly at the same point that the anode samples of first galvalume dross and second galvalume dross show no sign of aluminum passivation in cell off condition. Hence, continuous dissolution can be observed in the anode samples of first galvalume dross and second galvalume dross in the early stage of anodic polarization. Aluminum passivation could be observed from Fig 4(c) when potential surpasses nearly -0.98 VSCE in the anode samples of first galvalume dross and second galvalume dross during dynamic polarization. The mechanism of Al passive layer formation could be as follows

[0126] 2A1 = 2Al3++ 6e

[0127] O2 + 2H2O + 2e 4 OH~

[0128] 2A13++ 6 OH~ = 2A1(OH)3

[0129] 2A1(OH)3= AI2O3 + 3 H2O

[0130] The potentiodynamic behavior of the anode samples second galvalume dross follows the zinc anode behavior. The corrosion rates of the anode samples of first galvalume dross and second galvalume dross were observed to be 0.141 and 0.029 mm / y, respectively. The first one shows a higher corrosion rate than the second one.The selective dissolution of the aluminum-rich zones of the anode samples of first galvalume dross could be observed from the SEM micrograph, as shown in Fig 5(a). A uniform dissolution of the anode samples of second galvalume dross surface was observed after the potentiodynamic test, as shown in Fig 5(b). The anode samples of first galvalume dross surface after the PD test has been observed spongy and this is attributed to the selective leaching corrosion in comparison to the anode samples of first galvalume dross surface. The EDX elemental distribution is shown in Fig 5(c) and 5(d) for the anode samples of first galvalume dross and second galvalume dross, respectively. The elemental composition obtained from EDX analysis, as shown in Fig 5(e) for anode samples of first galvalume dross also confirms a substantial reduction in aluminum content in comparison to its original composition as shown in Table 2.

[0131] In the early stage, the aluminum-rich phase acts as an anode, and the zinc-rich phase behaves like a cathode. As the potential surpasses -1.0 VSCE, polarity reversal takes place due to the aluminum passivation. This behavior was observed for both the galvalume anodes.

[0132] Raman analysis of the corrosion products formed after the potentiodynamic test was done. The presence of Zn(OH)2at 145 cm-1, α- FeooH at 298 cm-1, amorphous Al2O3at 515 and 566 cm-1, and silicon (Si) at 945 and 1076 cm-1wavenumber was observed, as shown in Fig. 6(a).

[0133] 2.3.2 Electrochemical impedance spectroscopy (EIS) study

[0134] To better understand the corrosion behavior, EIS study has been carried out. The Nyquist plot, Bode magnitude plot, and Bode phase plot are shown in FIG 4(d-f), respectively. EIS study provides additional information related to corrosion behavior, diffusion, and coating or film properties. The electrical circuit fitting was done to the anode samples of first galvalume dross and second galvalume dross obtained from EIS study. The Electrical circuitsRs(CPEfRf)(CPEdlRct) and Rs(CPEfRf(CPEdlRct)) have been fitted for anode samples of first galvalume dross and second galvalume dros, respectively, as shown in Fig 4(g) and 4(h), respectively. Here, Rs, Rr, Ret, CPEi, and CPE2, are solution resistance, oxide film resistance, charge transfer resistance, constant phase element of oxide film, and constant phase element of electric double layer, respectively. The CPE is fitted in the circuit instead of the ideal capacitor. The non-ideal behavior of a capacitor is characterized by the CPE. The impedance of CPE can be calculated by using the following equation

[0135] ZCPE=[Yo(j<^>)n]1

[0136] Where y0is the frequency-independent real constant (Ω-1cm-2sn), j is the imaginary number, n is the CPE exponent, and co is the angular frequency. The value of n could be in the range of - 1 to 1. The pure capacitor, resistor, and pure inductor behavior are represented by n values 1, 0, and -1, respectively. The effective film capacitance (Cf) and double-layer capacitance (Cdl) could be obtained from the Brug's equation:

[0137] c

[0138]

[0139] di= Y”dl(R^ +

[0140] 1 zi-n\

[0141] cr = tr ’T ”1

[0142] The EIS results are summarized as shown in Table 4 below.

[0143] Rp, kQ Icorr,

[0144] Materials OCP, VSCE OCP, VCSE Ecorr, VSCE CR, mm / y cm2pA / cm2

[0145] First

[0146] galvalume -1.10 -1.18 0.660 -1.14 10.57 0.141 anode

[0147] Second

[0148] galvalume -1.03 -1.11 3.116 -1.02 2.08 0.029

[0149]

[0150] anodeLower solution resistance in case of the anode samples of first galvalume dross over the anode second galvalume dross clearly indicates higher dissolution of the former. The substantial presence of metal ions, preferably aluminum ions in the 3.5 wt% NaCl solution leads to the reduction of solution resistance. In EIS analysis two time constants were observed. One time constant is associated with the passive film formation at high frequency and the other one is for metallic corrosion at low frequency. The metallic corrosion time constant comes from the EDL. EDL has a resistive as well as a capacitive nature. The value constant phase element exponent (n) indicates the non-homogeneity of the test surface and the extent of corrosion. Inhomogeneity and corrosion increase as the value of n decreases, Hence, the first galvalume anode has considerably higher inhomogeneity on the surface due to the presence of pores and a higher corrosion rate than the second galvalume anode. The low value of the film resistance indicates poor film formation on the anode samples of first galvalume dross. It could be due to the significant difference in the OCP and the potential at which passive film formation starts whereas the anode samples of second galvalume dross OCP is close to the potential of passive film formation. Hence, the film resistance of the_anode samples of first galvalume dross is much higher than the anode samples of second galvalume dross. EIS parameters related to EDL show similar performance at low frequencies for anode samples of first galvalume dross and second galvalume dross. The value of chi-square is an indication of the precise fitting of data to the proposed electrical circuits.

[0151] 2.4 Anode Performance

[0152] The anode performance test is the most crucial experiment to find out the suitability of any material as a sacrificial anode for the cathodic protection of steel structures. All the anode performance parameters are summarized in Table 5 below:Table 5

[0153] Parameters First galvalume anode Second galvalume anode -1.10 V -1.03 V Open circuit potential (OCP)

[0154] Closed circuit potential at the -0.97 -0.868 end of 4thday (CCP, VSCE)

[0155] Theoretical anode capacity 1550.20 1458.82 (Qth, Ah / kg)

[0156] Experimental anode capacity 2255 860

[0157] (Qexp, Ah / kg)

[0158] 3.88 10.18 Consumption rate (kg / AY)

[0159] NA 58.95 Anode efficiency (%)

[0160] Reference anode efficiency 85.06 32.44

[0161]

[0162] (%)AI

[0163] The protection potential of underground and seashore steel structures is -0.78 VSCE. For any anode to act as a sacrificial anode must have the CCP at the end of the 4thday greater than -0.78 VSCE towards the anodic side. It can be observed from Table 5 that the CCPs of the anode samples of first galvalume dross and second galvalume dross at the end of the 4thday were observed as -0.97 VSCE and -0.868 VSCE, respectively. A positive shift in the CCP potential has been observed for both the galvalume anodes. At the end of the 4thday, a negative shift in the potential has been observed which could be due to the self-breaking of the passive film formed on both the galvalume anodes. The self-breaking of the passive film could be a technological advantage for both the anodes since this would enable no separate process for periodic reactivation. In case of aluminum anode, this is a usual practice of periodic reactivation of the surface.

[0164] The theoretical anode capacity (Qth, Ah / kg) of an alloy system can be calculated from the following equation derived from Faraday’s law:

[0165] > 26.80 * 103

[0166] Qth - 7kfjAWj^

[0167] \zi=i rij )

[0168]

[0169] Where i denotes the individual element of the alloy system, k is the total no of elements, fiis the fraction of element present in wt% in the alloy system, AW is the atomic weight of the ithelement, and m is the valency of the ithelement.

[0170] The experimental anode capacity (Qexp, Ah / kg) has been calculated by the following expression

[0171] ^

[0172]

[0173] exP=

[0174] Where C is the total charge in Ah passed during the anode performance test through the copper coulometer, and Wa is the weight loss in kg of the anode samples of first galvalume dross and second galvalume dross during the test.

[0175] The total charge passed through the copper coulometer in Ah can be calculated using the following expression

[0176] C = 0.8433 * WCu

[0177] Where WCuis the weight gain by the copper wire (g) during the anode performance test. The value of the experimental anode capacity of the anode samples of first galvalume dross lies in between the experimental anode capacity of the aluminum and magnesium anode whereas the experimental anode capacity of the anode samples of second galvalume dross lies in between the magnesium anode and zinc anode, as shown in Fig 6.

[0178] The consumption rate of the anode is defined as the material loss (kg) during a year (Y) when one ampere (A) of current is passed through the anode. It is measured in kg / AY. The anode efficiency is the ratio of the experimental anode capacity (QeXp)t0the theoretical anode capacity (Qth).

[0179] _ Qexp

[0180] 11“ " OuTFollowing the above equations, the anode samples of first galvalume dross efficiency was calculated to be more than 100% which is not possible. Hence, the method of calculation of anode efficiency as shown in Equation 13 is not applicable. The most probable reason could be that theoretical anode capacity calculation by using Faraday's law does not consider factors such as the significant presence of second alloying elements as in the current case, porosity, surface cracks, microstructure, surface inhomogeneity, passivity, and other possible factors. So, a new term is used to describe the performance of a sacrificial anode called reference anode efficiency (r]Ref, %). It is the ratio of the experimental anode capacity of a test anode to the experimental anode capacity of a reference anode such as aluminum or magnesium anode. „ > Qtest anode

[0181]

[0182] x reference anode

[0183] The reference anode must be selected in such a way that the value of the anode capacity of the test anode should not be higher than the standard reference anode. The aluminum anode is appropriate among all the reference anodes. So, the reference anode efficiencies of the anode samples of first galvalume dross and second galvalume dross were calculated using the aluminum anode as a reference, as shown in Table 5. Zn anode with an experimental anode capacity of 780 Ah / kg cannot be considered as a reference anode since the anode capacity is lower than that of the anode samples of and second galvalume dross. Now if aluminum anode is taken as a reference, the reference anode efficiencies of both standard Mg and standard Zn turn out to be 46.40 % and 26.42 %., respectively. The reference anode efficiency of the anode samples of second galvalume dross is 32.44 %. Hence, the anode samples of second galvalume dross lies between the Mg and Zn anode in terms of the reference anode efficiency. Similarly, the reference anode efficiency of the anode samples of first galvalume dross is 85 % which lies in between the Al and Mg anode in terms of the reference anode efficiency. The anodecapacities (Ah / kg) and reference anode efficiencies (%) of various anodes are also shown in Fig 6.

[0184] It could be observed based on anode capacity and reference anode efficiency that the anode performance of the anode samples of first galvalume dross which has aluminum-rich zones, is nearly close to the aluminum anode whereas the anode samples second galvalume dross performed like a zinc anode with passive layer formation characteristic of the aluminum anode. Hence, it could be concluded that the galvalume anode’s performance depends on the processing route, microstructure, composition, environment, surface inhomogeneities, and porosities.

[0185] These galvalume anodes are special on the grounds of composition. Generally, almost all the popular industrial sacrificial anodes have the presence of more than 95% of a single element and their overall performance revolves around the behavior of that element in the given environmental conditions. So, these industrial anodes could be easily characterized by the anode efficiency. In contrast, galvalume anodes have a significant presence of more than one element i.e., Al and Zn, where maximum element composition is limited to less than 60%. It has been observed that such anode's performance is difficult to characterize by anode efficiency. So, the reference anode efficiency term is used to characterize the anode performance which is a universal term applicable under any given conditions.

[0186] A discontinuous passive layer could be observed on the surface of anode samples of first galvalume dross and second galvalume dross after the end of the anode performance test, as shown in Fig 7(c) and 7(d), respectively. The passive layer on the anode samples of first galvalume dross has been observed to be thicker and more integrated to the surface with less exposed base anode surface in comparison to the anode samples of second galvalume dross. After cleaning the anodes, a uniform dissolution of the surface has been observed for both thegalvalume anodes, as shown in Fig 7(e) and 7(f). The Raman analysis has been performed on the corrosion product formed after the anode performance test. The presence of Zn(OH)2, α-FeooH, amorphous Al2O3, SiO, Al(OH)3, and silicon was observed the results are shown in Fig. 7(b).

[0187] Advantages:

[0188] The development and characterization of galvalume anodes, both the anode of first galvalume dross and second galvalume dros, open up a huge possibility of re-utilization of galvalume anodes towards quite efficient applications for sacrificial protection of steel structures.

[0189] The two different anodes are made from one dross source and can serve different environments.

[0190] The anode of first galvalume dross can find application to high resistance medium, whereas the anode of second galvalume dross one has the capability of use in moderate to low resistance medium.

[0191] The processing is quite simple, and the product manufacturing is sustainable too.

Claims

WE CLAIM:

1. A sacrificial anode for cathodic protection, comprising:Zinc, and Aluminium directly recovered from a galvalume dross.

2. The sacrificial anode for cathodic protection as claimed in claim 1, wherein the galvalume dross includes a galvalume dross having first composition or a galvalume dross having second composition.

3. The sacrificial anode for cathodic protection as claimed in claim 2, wherein the galvalume dross having first composition, comprises:Aluminium (Al) at about 56.2 ± 2 wt%, Zinc (Zn) at about 31.6 ± 2 wt%, Iron (Fe) at about 5.2 ± 2 wt%, Silicon (Si) at about 3.3 ± 1 wt% and rest non-traceable elements along with oxides.

4. The sacrificial anode for cathodic protection as claimed in claim 2, wherein the galvalume dross having second composition comprises:Aluminium (Al) at about 51.5 ± 2 wt%, Zinc (Zn) at about 38.9 ± 2 wt%, Iron (Fe) at about 1.5 ± 0.5 wt%, Silicon (Si) at about 4.9 ± 1 wt% and rest non-traceable elements along with oxides.

5. The sacrificial anode for cathodic protection as claimed in claim 3, wherein the sacrificial anode exhibits open circuit potential (OCP) being about -1.10 + 0.02 V (with respect to saturated calomel electrode).

6. The sacrificial anode for cathodic protection as claimed in claim 4, wherein the sacrificial anode exhibits open circuit potential (OCP) being about -1.03 ± 0.02V (with respect to saturated calomel electrode).

7. The sacrificial anode for cathodic protection as claimed in claim 3, wherein the sacrificial anode exhibits closed circuit potential (CCP) being about -0.97 + 0.05V as per DNV-RPB401, 2010 standard.

8. The sacrificial anode for cathodic protection as claimed in claim 4, wherein the sacrificial anode exhibits closed circuit potential (CCP) being about -0.868 ± 0.05V as per DNV-RPB401, 2010 standard.

9. The sacrificial anode for cathodic protection as claimed in claim 3, wherein the sacrificial anode exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1550.20 5.

10. The sacrificial anode for cathodic protection as claimed in claim 4, wherein the sacrificial anode exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1458.82 + io.

11. The sacrificial anode for cathodic protection as claimed in claim 3, wherein the sacrificial anode exhibits Experimental anode capacity (Qexp, Ah / kg) of about 2255 + 5.

12. The sacrificial anode for cathodic protection as claimed in claim 4, wherein the sacrificial anode exhibits Experimental anode capacity (Qexp, Ah / kg) of about 860 ± 10.

13. The sacrificial anode for cathodic protection as claimed in claim 3, wherein the sacrificial anode exhibits Consumption rate (kg / AY) about 3.88 + 0.2.

14. The sacrificial anode for cathodic protection as claimed in claim 4, wherein the sacrificial anode exhibits Consumption rate (kg / AY) about 10.18 ± 0.2.

15. The sacrificial anode for cathodic protection as claimed in claim 4, wherein the sacrificial anode exhibits Anode efficiency of about 58.95 + 5(%).

16. The sacrificial anode for cathodic protection as claimed in claim 3, wherein the sacrificial anode exhibits Reference anode efficiency of about 85.06 + 5 % (with reference to pure Al anode)17. The sacrificial anode for cathodic protection as claimed in claim 4, wherein the sacrificial anode exhibits Reference anode efficiency of about 32.44 ± 5 % (with reference to pure Al anode)18. A method for preparing a sacrificial anode for cathodic protection, the method comprising:heating a galvalume dross to a temperature of about 740 to about 780 deg C to obtain a molten zinc and aluminium residue; andpouring the molten zinc and aluminium residue directly into a mold to cast the sacrificial anode.

19. The method as claimed in claim 18, wherein the galvalume dross is heated for about 15 mins to about 20 mins.

20. The method as claimed in claim 18, wherein the galvalume dross is heated in a furnace.

21. The method as claimed in claim 18, wherein the sacrificial anode exhibits open circuit potential (OCP) being about -1.03 ± 0.02V (with respect to saturated calomel electrode).

22. The method as claimed in claim 18, wherein the sacrificial anode exhibits closed circuit potential (CCP) being about -0.868 ± 0.05V as per DNV-RPB401, 2010 standard.

23. The method as claimed in claim 18, wherein the sacrificial anode exhibits the theoretical anode capacity (Qth, Ah / kg) of about 1458.82 ± 10.

24. The method as claimed in claim 18, wherein the sacrificial anode exhibits Experimental anode capacity (Qexp, Ah / kg) of about 860 ± 10.

25. The method as claimed in claim 18, wherein the sacrificial anode exhibits Consumption rate (kg / AY) about 10.18 ± 0.2.

26. The method as claimed in claim 18, wherein the sacrificial anode exhibits Anode efficiency of about 58.95 ± 5 (%)27. The method as claimed in claim 18, wherein the sacrificial anode exhibits reference anode efficiency of about 32.44 ± 5 % (with reference to pure Al anode).

28. The method as claimed in claim 18, wherein the galvalume dross comprises:Aluminium (Al) about 56.2 ± 2, Zinc (Zn) about 31.6 ± 2, Iron (Fe) about 5.2 ± 2, Silicon (Si) about 3.3 ± 1 and rest non-traceable elements along with oxides.

29. The method as claimed in claim 18, wherein the galvalume dross includes a galvalume dross having second composition comprising:Aluminium (Al) about 51.5 ± 2, Zinc (Zn) about 38.9 ± 2, Iron (Fe) about 1.5 ± 0.5, Silicon (Si) about 4.9 ± 1 and rest non-traceable elements along with oxides.

30. A sacrificial anode for cathodic protection, comprising:Zinc, and Aluminium directly recovered from a galvalume dross having first composition comprising:Aluminium (Al) at about 56.2 ± 2 wt%, Zinc (Zn) at about 31.6 ± 2 wt%, Iron (Fe) at about 5.2 ± 2 wt%, Silicon (Si) at about 3.3 ± 1 wt% and rest non-traceable elements along with oxides.

31. A sacrificial anode for cathodic protection, comprising:Zinc, and Aluminium directly recovered from a galvalume dross having second composition comprises:Aluminium (Al) at about 51.5 ± 2 wt%, Zinc (Zn) at about 38.9 ± 2 wt%, Iron (Fe) at about 1.5 ± 0.5 wt%, Silicon (Si) at about 4.9 ± 1 wt% and rest non-traceable elements along with oxides.

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