PENGARUH KADAR SALINITAS AIR TERHADAP LAJU KOROSI BAJA ST 60

Daerah perairan dapat menimbulkan risiko serangan korosi yang lebih tinggi terutama pada lingkungan perairan yang mengandung salinitas atau salinitas, umumnya korosi yang terjadi di perairan dapat menyerang logam, salah satunya adalah baja ST 60 yang banyak digunakan sebagai bahan konstruksi dalam konstruksi bangunan. pelabuhan, jembatan, poros baling-baling, dan aplikasi lain yang terkait dengan lingkungan perairan. Dampak yang ditimbulkan adalah logam dapat mengalami serangan korosi dengan cepat akibat berinteraksi dengan lingkungan air yang mengandung salinitas sehingga logam tersebut akan mengalami kerusakan dan kehilangan sifat teknisnya. Pada penelitian pengujian perendaman dilakukan dengan 3 minggu terus menerus dan 3 minggu (dengan 2 minggu perendaman kemudian 1 minggu tidak terendam) menggunakan air laut yang berasal dari pantai takisung, pelaihari dengan salinitas 2,48% dan air payau yang berasal dari dataran tinggi banjarmasin dengan salinitas 1,25%. Hasil penelitian menunjukkan laju korosi tertinggi terjadi pada 3 minggu perendaman terus menerus dengan air laut yang memiliki salinitas 2,48% dan jenis korosi yang terbentuk adalah korosi seragam. Water areas can pose a higher risk of corrosion attack, especially in aquatic environments that contain salinity or salinity, generally corrosion that occurs in the waters can attack metals, one of which is ST 60 steel which is widely used as construction material in the construction of ports, bridges, propeller axis, and other applications related to the aquatic environment. The impact caused is that the metal can experience corrosion attacks quickly due to interacting with the water environment containing salinity so that the metal will experience damage and lose its technical properties. In the study immersion testing was carried out with 3 weeks continuously and 3 weeks (with 2 weeks immersion then 1 week not submerged) using seawater originating from takisung beach, pelaihari with salinity of 2.48% and brackish water originating from the high land area of banjarmasin with a salinity of 1.25%. The results showed the highest corrosion rate occurred at 3 weeks of continuous immersion with seawater which had a salinity of 2.48% and the type of corrosion formed was uniform corrosion.

Usage of Barkhausen Noise for Assessment of Corrosion Damage on Different Low Alloyed Steels

This study deals with corrosion damage of low alloyed feritic steels of variable strength. Three different steels of nominal yield strength 235, 700 and 1100 MPa were subjected to the variable degree of corrosion attack developed in the corrosion chamber under a neutral salt spray (NSS) atmosphere. The corrosion damage was investigated by the use of conventional metallographic observations when the thickness of corroded layer was quantified. Moreover, non-destructive magnetic technique, based on Barkhausen noise, was also employed. It was found that the rate of corrosion damage decreases along with the increasing number of days in the chamber. The similar evolution can be also found for Barkhausen noise emission and the extracted parameters from the emission. It can be reported that conventional rms value of Barkhausen noise signal as well as FWHM (full width at half maximum of Barkhausen noise envelope) can be linked with the corrosion extent, especially in the early phases of corrosion attack. The PP (peak position of Barkhausen noise envelope) values exhibit poor sensitivity.

Duplex Steels Used in Building Structures and Their Resistance to Chloride Corrosion

Welded structures made of duplex steels are used in building applications due to their resistance to local corrosion attack initiated by chlorides. In this paper, the material and technological factors determining the corrosion resistance are discussed in detail. Furthermore, recommendations are formulated that allow, in the opinion of the authors, to obtain a maximum corrosion resistance for welded joints. The practical aspects of corrosion resistance testing are also discussed, based on the results of qualification tests. This work is of a review character. The conclusions and practical recommendations are intended for contractors and investors of various types of structures made of the duplex steel. The recommendations concern the selection and use of duplex steels, including the issues of metallurgy, welding techniques, and corrosion protection.

A Field Study of Atmospheric Corrosion of Carbon Steel after Short Exposure in Pelabuhan Ratu, West Java Province, Indonesia

The investigation of atmospheric corrosion of mild carbon steel as representative of offshore infrastructure has been carried out in the marine tropical of Pelabuhan Ratu, West Java, Indonesia. They are exposed up to 76 days of periods, and their corrosion rates are determined according to ASTM G1-03. The surface morphology, the elemental compositions and compounds were observed using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The environmental parameters of the test site are monitored during exposure, such as air temperature, relative humidity (RH), airborne salinity and dew temperature. Based on the results, the corrosion rates of steels were 2.79 and 2.8 mpy within the 27 and 76 days exposures, respectively. The presence of chloride deposition on the surface of steel can increase the severity of corrosion. Moreover, the detrimental effect of chloride was observed in rust product, which was covered by an oxygen element. The main phases of rust products present were magnetite (Fe3O4) and hematite (α-Fe2O3.H2O). Several cracks were observed in the rust layer, which tended to exfoliate and lose adherence and protectiveness from further corrosion attack. HIGHLIGHTS The presence of chloride deposition on the surface of steel can increase the severity of corrosion. The severity of corrosion attack mainly depends on the exposure time and some climatic parameters, such as relative humidity (RH), air temperature and chloride airborne. The uniform distribution of the chloride tends to increase the production of ferrous chloride in high RH condition and the aqueous layer deposited on carbon steel. There are two phases on corroded carbon steel such as hematite (α-Fe2O3.H2O) and Magnetite (Fe3O4) after exposure GRAPHICAL ABSTRACT

A Peridynamic Model for Crevice Corrosion Damage

A new peridynamic (PD) model for crevice corrosion damage is introduced and cross-validated with experimental results reported in the literature. The model defines a simple metal ion concentration-dependent corrosion rate along the metal-electrolyte interface. Crevice problems have ratios of gap-to-length of 1/100 or lower. To increase the computational efficiency when having a domain with an extreme aspect ratio, the PD formulation with spherical horizons is modified to accommodate arbitrary-shape horizons. The model is validated against experimental results on immersed bolted washers. The PD simulations predict the observed corrosion kinetics, and the deepest corrosion trenches form at a critical distance from the mouth of the crevice. The location of the most severe corrosion attack does not have to be specified as an input. Instead, it results directly from solving the problem with PD. The evolution of crevice corrosion damage is autonomous in PD, and only the geometry, initial, and boundary conditions control the evolution of the corrosion process.

Effect of solution aggressiveness on the crack - growth resistance and cracking mechanism of AA2024-T3

Aluminium alloy 2024-T3 was examined – using a range of microscopy techniques – at the early stages of corrosion attack to investigate the corrosion-induced cracking mechanism. Two different corrosive environments, exfoliation corrosion (EXCO) and 3.5 % wt. NaCl, were used for the exposure of tensile and pre-notched compact-tension C(T) specimens of AA2024-T3. Different embrittlement mechanisms are noticed for the two investigated corrosive environments. Significant intergranular corrosion (IGC) and grain boundary embrittlement is evident in the specimens exposed to EXCO solution, while this was not the case for the milder solution; comprising of 3.5 % wt. NaCl. With regards to the milder solution, corrosion attack is not restricted to the grain boundary, but evolves transgranularly to the neighbouring grains of the IGC attacked region and, consequently, the grain boundary strength in the direct vicinity is not notably affected. The extent of secondary cracks – after the exposure of C(T) specimens to EXCO solution and the subsequent crack-growth resistance evaluation – were found to correlate with the diameter of the plastically affected zone (≈ 3.78 ± 0.04 mm). Additionally, the depth of these cracks was found to correlate well with the thickness of the intergranular fracture surface, giving evidence that the secondary cracks form due to grain boundary embrittlement; probably attributed to hydrogen embrittlement phenomena.

A model study on controlling dealloying corrosion attack by lateral modification of surfactant inhibitors

Detrimental corrosion is an ever-concerning challenge for metals and alloys. One possible remedy is to apply organic corrosion inhibitors. Despite progress in molecular assembly and inhibitor research, better mechanistic insight on the molecular level is needed. Here we report on the behavior of well-defined artificial molecular interfaces created by micro-contact printing of thiol-inhibitor molecules and subsequent backfilling. The obtained heterogeneity and defects trigger localized dealloying-corrosion of well-defined Cu3Au surfaces. The stability of applied inhibitor molecules depends on alloy surface morphology and on intermolecular forces of the molecular layers. On extended terraces, dealloying preferentially starts at the boundary between areas composed of the two different chain-length inhibitor molecules. Inside of the areas hardly any nucleation of initial pits is visible. Step density strongly influences the morphology of the dealloying attack, while film heterogeneity avoids cracking and controls molecular-scale corrosion attack. The presented surface-science approach, moreover, will ultimately allow to verify the acting mechanisms of inhibitor-cocktails to develop recipes to stabilize metallic alloy surfaces.

Experimental Investigation and Artificial Neural Network Based Prediction of Bond Strength in Self-Compacting Geopolymer Concrete Reinforced with Basalt FRP Bars

The current research on concrete and cementitious materials focuses on finding sustainable solutions to address critical issues, such as increased carbon emissions, or corrosion attack associated with reinforced concrete structures. Geopolymer concrete is considered to be an eco-friendly alternative due to its superior properties in terms of reduced carbon emissions and durability. Similarly, the use of fibre-reinforced polymer (FRP) bars to address corrosion attack in steel-reinforced structures is also gaining momentum. This paper investigates the bond performance of a newly developed self-compacting geopolymer concrete (SCGC) reinforced with basalt FRP (BFRP) bars. This study examines the bond behaviour of BFRP-reinforced SCGC specimens with variables such as bar diameter (6 mm and 10 mm) and embedment lengths. The embedment lengths adopted are 5, 10, and 15 times the bar diameter (db), and are denoted as 5 db, 10 db, and 15 db throughout the study. A total of 21 specimens, inclusive of the variable parameters, are subjected to direct pull-out tests in order to assess the bond between the rebar and the concrete. The result is then compared with the SCGC reinforced with traditional steel bars, in accordance with the ACI 440.3R-04 and CAN/CSA-S806-02 guidelines. A prediction model for bond strength has been proposed using artificial neural network (ANN) tools, which contributes to the new knowledge on the use of Basalt FRP bars as internal reinforcement in an ambient-cured self-compacting geopolymer concrete.

Analysis of Corrosion Resistant Steel Coating Using Hot Dip Galvanization Method and Polarization / Tafel Test

Hot Dip Galvanization (HDG) is a method of plating steel by immersing liquid zinc. However, in this study, HDG was tried by dipping steel in a solution of cast aluminum waste, after being coated with galvanizing and graphene. Furthermore, the corrosion test is carried out using the tafel or polarization test aid. The aim of this research is to protect the corrosion attack on steel by means of HDG in a solution of cast aluminum waste, after being coated with galvanizing and graphene. The solution in the tafel test used NaCl solution. The results obtained were the least corrosion attacks on steel with a galvanic coating and graphene. Meanwhile, HDG with cast aluminum waste is not significant to protect corrosion on steel.