Surface engineering is a vital aspect of manufacturing industries owing to its benefits both in surface protection and aesthetics. It has been extensively used in various industries to guard against corrosion which is a naturally occurring and highly undesirable phenomenon. Present research has endeavored to analyze protection of ASTM A516 (Grade 70) from corrosion through surface engineering. Different methods of surface treatment and conversion coating were carried out to efficiently enhance corrosive protection. Comparative analysis of various samples was conducted to analyze their ability to resist corrosion. Samples with surface treatment followed by conversion coating were found to be effective even against 0.7% aqueous sulfuric acid with no significant cracks in the coating layer. On the other hand, conversion coated only samples showed protection against 0.35% acid. The coating of conversion coated only samples was found to have gaps/ cracks as indicated by 3% Cupric Sulfate whereas no such gaps were found in surface treated samples. Optical microscopy identified a more uniform coating thickness for surface treated samples in comparison with conversion coated only samples. In depth morphology analysis using SEM highlighted that surface treated samples had low porosity preventing the corrosion elements to reach the substrate thereby implementing higher corrosion potential

Khan, Muhammed Ali

Nisar, Salman

Sha, Aqueel

Yusuf, Adeel

11th International Conference on Through-life Engineering Services - TESConf 2022, 8-9 November 2022, Cranfield UKSurface engineering is a vital aspect of manufacturing industries owing to its benefits both in surface protection and aesthetics. It has been extensively used in various industries to guard against corrosion which is a naturally occurring and highly undesirable phenomenon. Present research has endeavored to analyze protection of ASTM A516 (Grade 70) from corrosion through surface engineering. Different methods of surface treatment and conversion coating were carried out to efficiently enhance corrosive protection. Comparative analysis of various samples was conducted to analyze their ability to resist corrosion. Samples with surface treatment followed by conversion coating were found to be effective even against 0.7% aqueous sulfuric acid with no significant cracks in the coating layer. On the other hand, conversion coated only samples showed protection against 0.35% acid. The coating of conversion coated only samples was found to have gaps/ cracks as indicated by 3% Cupric Sulfate whereas no such gaps were found in surface treated samples. Optical microscopy identified a more uniform coating thickness for surface treated samples in comparison with conversion coated only samples. In depth morphology analysis using SEM highlighted that surface treated samples had low porosity preventing the corrosion elements to reach the substrate thereby implementing higher corrosion potential.DMG Mor

Cranfield CERES

11th International Conference on Through-life Engineering Services – TESConf2022 8-9 November 2022, Cranfield UK Peer-review under responsibility of the Programme Chair of the 11th International Conference on Through-life Engineering Services. © Licence Under: CC-BY-4.0 Surface analysis of conversion coating of ASTM A 516 Muhammad Ali Khan1,2*, Aqueel Shah2, Adeel Yusuf2, Salman Nisar2 1Department of Mechanical Engineering (CEME), National University of Sciences and Technology (NUST), Islamabad, 44000, Pakistan. 2Pakistan Naval Engineering College (PNEC), National University of Sciences and Technology (NUST), Pakistan. * Corresponding author. Tel.: +923335248284; fax: +925154444350; E-mail address: mak.ceme@ceme.nust.edu.pk Abstract Surface engineering is a vital aspect of manufacturing industries owing to its benefits both in surface protection and aesthetics. It has been extensively used in various industries to guard against corrosion which is a naturally occurring and highly undesirable phenomenon. Present research has endeavored to analyze protection of ASTM A516 (Grade 70) from corrosion through surface engineering. Different methods of surface treatment and conversion coating were carried out to efficiently enhance corrosive protection. Comparative analysis of various samples was conducted to analyze their ability to resist corrosion. Samples with surface treatment followed by conversion coating were found to be effective even against 0.7% aqueous sulfuric acid with no significant cracks in the coating layer. On the other hand, conversion coated only samples showed protection against 0.35% acid. The coating of conversion coated only samples was found to have gaps/ cracks as indicated by 3% Cupric Sulfate whereas no such gaps were found in surface treated samples. Optical microscopy identified a more uniform coating thickness for surface treated samples in comparison with conversion coated only samples.  In depth morphology analysis using SEM highlighted that surface treated samples had low porosity preventing the corrosion elements to reach the substrate thereby implementing higher corrosion potential.  Keywords: ASTM A 516 (Grade 70); Corrosion; Surface engineering; Conversion coating 1. Introduction Corrosion is a highly undesirable phenomenon  which occurs naturally at varying rates depending upon the availability of mainly basic and then catalyzing agents [1][2] Nomenclature EDS Energy Dispersive X-ray Spectroscopy RPM Revolutions per Min  SEM Scanning Electron Microscope Corrosion of iron and steel is known as rusting which produces Fe2O3 (rust) as final product. The overall process comprises of a number of reaction, collectively as redox reactions  [3]. Corrosion of carbon steel causes physical degradation which, annually, results in huge financial losses worldwide  [4]. Coatings are an effective method of enhancing corrosion resistance for various materials [5]. It can serve the dual purpose of surface protection and aesthetics [6]. Various type of coating technologies are used worldwide [7]–[9]. Conversion coating is a extensively used process owing to its simple and economical procedure as well as enhanced protection [10]. There are different types of conversion coating processes with varying effectiveness mainly depending upon the treatment solution and process time, among other factors. Past researchers have used different methods of conversion coatings to analyze their resistance potential. In few instances, surface was mechanically treated in combination with coating to enhance the barrier towards corrosion. Zeng et al [11] concluded that phosphate coating not only improves the biocompatibility of We43 alloy but also adds to the corrosion resistance. In another related study, it was found that effectiveness of phosphating can be further improved by adding benzotrizole  [12]. Jinlong et al [5] investigated the corrosion resistance of NiTi shape memory alloy in NaCl, H2SO4 and borate buffer solution. The corrosion protection of different samples was attributed to donor concentration in conversion coating and film thickness. Ghaziof et al [13] studied the effects of chromium carbon coating in combination with mechanical and electro polishing procedures. It was found that steel gets a high corrosion barrier as a result of coating. The pre-coating surface treatment ensured a defect free coating thereby improving the protection against corrosion. Ganesh et al [14] carried out thermo-mechanical treatment on SAE 304 stainless steel. XRD analysis highlighted the enhanced inter granular corrosion resistance and materials potential against sensitization. In another related research, Onofre et al [15] found that in addition to corrosion protection, conversion coating enhanced the adhesiveness effect. Literature also highlights that Magnetite coating (Fe3O4) have been researched on Muhammad Ali Khan (2022) 2  different materials using various methods[16]. Nagode et al. [17] deposited magnetite coating on grey cast iron plates which was found to be stable at elevated temperatures. Possibility of formation of hematite was also observed owing to the oxidation of magnetite layer. A similar coating was made on cast iron in the presence of chromium and silicon by Arab and Rahimi [18]. It was concluded that the resulting magnetite coatings was able to withstand 150 hours of salt spray test. In another related study [19], carbon steel was coated with magnetite under varying temperature, voltage and electrolytic composition conditions. Resultantly, coating thickness was found to be a function of input parameters.           2. Design of experiment 2.1 Specimen material Optical emission spectroscopy of the selected specimen (ASTM A 516 grade 70) material was carried out with results given in Table 1. ASTM A 516 was selected owing to its worldwide usage in various industries. Its superior mechanical properties [20] as shown in Table 2, makes it a preferred choice specially in construction sector.  Table 1. ASTM A516 - Chemical Composition Element Percentage Mn 0.85 – 1.2% Si 0.15 – 0.40% C 0.10 – 0.28% P 0.010 – 0.035% S 0.010 – 0.035% Fe balance   Table 2 ASTM A516 - Mechanical properties [20] Property Value Tensile Strength 511 N/mm2 Yield Strength 424 N/mm2 Elongation 24%  2.2 Sample preparation Work specimen was cut into samples size of 10 inches' length and 6 inches' width, having a thickness of 0.12 inches'. Two different batches were made for comparison. The samples in each batch were given separate treatment as per the categorization shown in Table 3. Type 1 samples were given hot alkaline bath. During this process, these samples were kept for 45 minutes in aqueous mixture of sodium nitrate (NaNO3) and sodium hydroxide (NaOH) in a ratio of 1:3 at 130°C. As a result, samples were coated with coating of magnetite (Fe3O4). Type 2 samples were first surface treated by grinding them with emery paper grinder (grit size - 300 µm) at 3000 RPM. These samples then underwent conversion coating process with hot alkaline bath, as explained earlier. These samples are as shown in Fig. 1.  Table 3 Specimen types Specimen Surface Treatment Conversion Coating Type 1 ✘ ✓ Type 2 ✓ ✓   Type 1  Type 2 Fig. 1 Types of samples  3. Coating tests Magnetite coating was tested for its corrosion resistance and uniformity using stability and continuity test respectively. Literature indicates the use of sulfuric acid for stability test which acts as corrosion accelerator [21]. Various materials including Stainless Steel (type 304) [22], Titanium [23] and concrete [24] have been tested using such tests. Similarly, cupric sulfate solution has been used in the past to check uniformity of conversion coatings [25].   3.1 Stability test Stability test was conducted to ascertain the effectiveness of the coating process. It signifies the Muhammad Ali Khan (2022) 3  strength of coating under corrosive environment. Drops of 0.175% aqueous solution of sulfuric acid were put on the coated surface. The acid takes away any poor or low quality coatings on contact. It was found that neither of the coatings was washed away by the acid. In the next step stronger 0.35% solution was used which too was unable to dislodge the coatings. In the third stage 0.7% acidic solution removed coating from type 1 sample but type 2 coating kept intact. Results displayed in Fig. 2.      Type 1 Type 2 Fig. 2 Stability test 3.2 Continuity test Continuity test was conducted to find the presence of gaps and cracks present in the coating. Such defects can result during the initial coating procedure. In this test 3% Cupric Sulfate solution drops were put on the sample surface for 30 seconds. Cracks or gaps in the coating were highlighted by red color copper deposits. Results are displayed in Fig. 3.      Type 1 Type 2 Fig. 3 Continuity test Drops of cupric sulfate on type 1 sample reflected red color confirming the presence of copper deposits. It was indication of the presence of cracks and/or pores. However, no significant deposits were seen on type 2 samples. It was concluded that type 2 samples had continuous and defect free coating.      4. Surface analysis 4.1 Cross sectional analysis Optical microscopy of the samples was conducted for further analysis of coating. The cross section of samples was observed to check the coatings for uniformity. Fig. 4 shows the cross sectional view of type 1 and type 2 samples.       Type 1   Type 2 Fig. 4 Cross sectional view of samples The images show that type 1 has a coating with varying thickness from 26 µm to 45 µm. The base surface is uneven with few sharp edges and corners. Coating thickness of type 2 sample was found to be more uniform with thickness from 38 µm to 44 µm. Substrate had a much leveled surface owing to the surface treatment carried out before conversion coating.      4.2 Morphology analysis   SEM analysis was carried out to observe the surface morphology of samples as shown in Fig. 5. Porosity on the surface allows corrosion ingredients to act effectively at surface and sub-surface levels to initiate and catalyze the rusting process. Type 1 showed high amount of porosity and unevenness. Porosity of type 2 sample was found to be much lower due to the grinding surface treatment.     40.00 µm 38.00 µm 45.00 µm 31.00 µm Copper deposits No Copper deposits Coating dislodged  Coating Intact  Muhammad Ali Khan (2022) 4   Type 1  Type 2 Fig. 5 SEM images EDS analysis of type 1 sample indicated the presence of Fe2O3 (oxide known as rust) and other corrosion by products in addition to coating material Fe3O4.  In case of type 2 sample no corrosion elements were present whereas a uniform magnetite (Fe3O4) layer was detected.   5. Conclusion Present research has chalked out the following conclusions:  Conversion coating of magnetite (Fe3O4) is an effective way to protect against corrosion. The protection can be further enhanced by surface treatment through grinding prior to the coating process.    Coating layer of magnetite (Fe3O4) displayed effective protection against up to 0.35% aqueous sulfuric acid solution in stability test. Coating on ground surface was found effective even against 0.7% acidic solution. SEM analysis revealed that surface grinding removes surface pores which otherwise are prone to initiate corrosion process.  The coating of unground surface displayed some gaps in continuity tests using 3% Cupric Sulfate solution. However, no such gaps were present in the coating layer of ground samples. This is due to the uniform coating thickness of surface treated samples varying from 38 µm to 44 µm as observed in Optical microscopy images. On the other hand, in case of untreated samples the coating thickness varied from 26 µm to 45 µm.   References [1] X. Guo, K. Chen, W. Gao, Z. Shen, P. Lai, and L. Zhang, “A research on the corrosion and stress corrosion cracking susceptibility of 316L stainless steel exposed to supercritical water,” Corros. Sci., vol. 127, no. 2016, pp. 157–167, 2017, doi: 10.1016/j.corsci.2017.08.027. [2] M. A. Amin and M. M. Ibrahim, “Corrosion and corrosion control of mild steel in concentrated H2SO4 solutions by a newly synthesized glycine derivative,” Corros. Sci., vol. 53, no. 3, pp. 873–885, 2011, doi: 10.1016/j.corsci.2010.10.022. [3] L. L. Shreir, “Basic concepts of corrosion,” Shreir’s Corros., vol. 1, pp. 89–100, 2010, doi: 10.1016/B978-044452787-5.00006-8. [4] B. N. Popov, Corrosion Engineering: Principles and Solved Problems. 2015. doi: 10.1016/C2012-0-03070-0. [5] L. Jinlong, L. Tongxiang, W. Chen, D. L.-M. S. And, and U. 2016, “Surface corrosion enhancement of passive films on NiTi shape memory alloy in different solutions,” Mater. Sci. Eng. C, pp. 192–197. [6] H. R. Asemani, P. Ahmadi, A. A. Sarabi, and H. Eivaz Mohammadloo, “Effect of zirconium conversion coating: Adhesion and anti-corrosion properties of epoxy organic coating containing zinc aluminum polyphosphate (ZAPP) pigment on carbon mild steel,” Prog. Org. Coatings, vol. 94, pp. 18–27, 2016, doi: 10.1016/j.porgcoat.2016.01.015. [7] L. Guo et al., “A black conversion coating produced by hot corrosion of magnesium with deep eutectic solvent membrane,” Surf. Coatings Technol., vol. 357, no. August 2018, pp. 833–840, 2019, doi: 10.1016/j.surfcoat.2018.10.062. [8] M. Fenker, M. Balzer, and H. Kappl, “Corrosion protection with hard coatings on steel: Past approaches and current research Muhammad Ali Khan (2022) 5  efforts,” Surf. Coatings Technol., vol. 257, pp. 182–205, 2014, doi: 10.1016/j.surfcoat.2014.08.069. [9] P. Niranatlumpong, H. K.-S. and C. Technology, and U. 2006, “Improved corrosion resistance of thermally sprayed coating via surface grinding and electroplating techniques,” Surf. Coat. Technol., vol. 201, pp. 737–743. [10] P. Riazaty, R. Naderi, and B. Ramezanzadeh, “Enhancement of the Epoxy Coating Corrosion/Cathodic Delamination Resistances on Steel by a Samarium Based Conversion Coating,” J. Electrochem. Soc., vol. 166, no. 13, pp. C353–C364, 2019, doi: 10.1149/2.0151913JES/META. [11] Q. Zeng, J. Zhang, H. Cheng, L. Chen, and Z. Qi, “Corrosion properties of steel in 1-butyl-3-methylimidazolium hydrogen sulfate ionic liquid systems for desulfurization application,” RSC Adv., vol. 7, no. 77, pp. 48526–48536, 2017, doi: 10.1039/c7ra09137k. [12] E. Banczek, P. Rodrigues, I. C.-S. and C. Technology, and U. 2006, “Investigation on the effect of benzotriazole on the phosphating of carbon steel,” Surf. Coat. Technol., vol. 201, pp. 3701–3708, 2006. [13] S. Ghaziof, K. Raeissi, M. G.-S. and C. Technology, and U. 2010, “Improving the corrosion performance of Cr–C amorphous coatings on steel substrate by modifying the steel surface preparation,” Surf. Coat. Technol., vol. 205, pp. 2174–2183, 2010. [14] P. Ganesh et al., “Enhancement of intergranular corrosion resistance of type 304 stainless steel through a novel surface thermo-mechanical treatment,” Surf. Coatings Technol., vol. 232, pp. 920–927, Oct. 2013, doi: 10.1016/J.SURFCOAT.2013.06.124. [15] E. Onofre-Bustamente, … M. D.-C.-S. and C., and U. 2007, “Characteristics of blueing as an alternative chemical conversion treatment on carbon steel,” Surf. Coat. Technol., vol. 201, pp. 4666–4676, 2007. [16] A. R. Reghuraj and K. K. Saju, “Black oxide conversion coating on metals: A review of coating techniques and adaptation for SAE 420A surgical grade stainless steel,” Mater. Today Proc., vol. 4, no. 9, pp. 9534–9541, 2017, doi: 10.1016/j.matpr.2017.06.219. [17] A. Nagode, G. Klančnik, H. Schwarczova, B. Kosec, M. Gojić, and L. Kosec, “Analyses of defects on the surface of hot plates for an electric stove,” Eng. Fail. Anal., vol. 23, pp. 82–89, 2012, doi: 10.1016/j.engfailanal.2012.03.001. [18] N. Arab and M. Rahimi Nezhad Soltani, “A Study of Coating Process of Cast Iron Blackening,” J. Appl. Chem. Res., vol. 9, pp. 13–23, 2009. [19] T. D. Burleigh, T. C. Dotson, K. T. Dotson, S. J. Gabay, T. B. Sloan, and S. G. Ferrell, “Anodizing Steel in KOH and NaOH Solutions,” J. Electrochem. Soc., vol. 154, no. 10, p. C579, 2007, doi: 10.1149/1.2767417. [20] A. B. Ibrahim, F. A. Al-Badour, A. Y. Adesina, and N. Merah, “Effect of process parameters on microstructural and mechanical properties of friction stir diffusion cladded ASTM A516-70 steel using 5052 Al alloy,” J. Manuf. Process., vol. 34, no. February, pp. 451–462, 2018, doi: 10.1016/j.jmapro.2018.06.020. [21] J. Monteny et al., “Chemical, microbiological, and in situ test methods for biogenic sulfuric acid corrosion of concrete,” Cem. Concr. Res., vol. 30, no. 4, pp. 623–634, 2000, doi: 10.1016/S0008-8846(00)00219-2. [22] A. M. Al-Mayouf, A. A. Al-Suhybani, and A. K. Al-Ameery, “Corrosion inhibition of 304SS in sulfuric acid solutions by 2-methyl benzoazole derivatives,” Desalination, vol. 116, no. 1, pp. 25–33, 1998, doi: 10.1016/S0011-9164(98)00054-X. [23] I. N. Andijani, S. Ahmad, and A. U. Malik, “Corrosion behavior of titanium metal in the presence of inhibited sulfuric acid at 50°C,” Desalination, vol. 129, no. 1, pp. 45–51, 2000, doi: 10.1016/S0011-9164(00)00050-3. [24] E. K. Attiogbe and S. H. Rizkalla, “Response of concrete to sulfuric acid attack,” ACI Mater. J., vol. 85, no. 6, pp. 481–488, 1988, doi: 10.14359/2210. Muhammad Ali Khan (2022) 6  [25] X. Tan and F. Nan, “Performance of Modified Nano-SiO2 Composite Phosphating Coating on the Surface of Steel,” IOP Conf. Ser. Mater. Sci. Eng., vol. 840, no. 1, 2020, doi: 10.1088/1757-899X/840/1/012002.      

Surface analysis of conversion coating of ASTM A 516

https://dspace.lib.cranfield.ac.uk/bitstream/1826/18680/1/TESConf_2022_paper_7600_ia.pdf

Surface analysis of conversion coating of ASTM A 516

Abstract

Similar works

Full text

Available Versions

Cranfield CERES