Effect of weld line direction and paint orientation on corrosion and paint deterioration characteristics of welded part of steel

One thousand two hundred cycles of accelerated exposure experiment with combined salt water spray simulating atmospheric corrosion was performed for investigating the effect of weld line direction and paint orientation on the corrosion and paint deterioration characteristics of welded part of the steel. The corrosion depth of the weld toe of transverse weld line became 1.35 times as large as that of the base metal part because of the remained salt water on the weld toe. The coating thickness at the weld toe became thin by vertically painting on the transverse weld line. When the scribe line was installed at the thin painted weld toe under the transverse weld line, the paint blister area became 15% larger than that of the base metal part. The paint coating thickness at the weld toe in different weld line directions and paint orientations should be confirmed and ensured from the viewpoints of manufacturing and maintaining steel structures.     

海洋大气中钢结构用锌铝伪合金喷涂层防腐蚀体系

高铝含量的锌铝伪合金喷涂层可采用大功率二次风熔丝喷涂工艺获得,适用于海洋大气中的钢结构。长达16 000 h的加速盐雾试验表明,该涂层是一种长效防腐涂层,据推算,在海洋大气条件下,其寿命可达80年。为确保防腐蚀效果,应提高锌铝伪合金喷涂层中铝的含量,经测定,我国目前锌铝伪合金喷涂层表面的铝、锌氧化物体积分数之和已达到70%。     

Triazole derivatives as corrosion inhibitors for mild steel in hydrochloric acid solution

The title compounds 1-(4,5-dihydro-3-phenyl pyridine-1-yl)-2-(1H-1,2,4-triazole-1-yl)ethyl ketones were studied as a corrosion inhibitor in a mild steel in 1 mol /L hy-drochloric acid solution using weight loss measurement,potentiodynamic polariza-tion,and electrochemical impedance spectroscopy(EIS).Results indicated that these compounds had excellent inhibition properties.Polarization curves indicated that the inhibitor behaved mainly as mixed-type inhibitor.The EIS results showed that the charge transfer ...     

Sodium phthalamates as corrosion inhibitors for carbon steel in aqueous hydrochloric acid solution

Three compounds of N-alkyl-sodium phthalamates were synthesized and tested as corrosion inhibitors for carbon steel in 0.5 M aqueous hydrochloric acid. Tests showed that inhibitor efficiencies were related to aliphatic chain length and dependent on concentration. N-1-n-tetradecyl-sodium phthalamate displayed moderate efficiency against uniform corrosion, 42–86% at 25 °C and 25–60% at 40 °C. Tests indicated that compounds behave as mixed type inhibitors where molecular adsorption on steel followed Langmuir isotherm, whereas thermodynamic suggested that a physisorption process occurred. XPS analysis confirmed film formation on surface, where Fe⁺² complexes and Fe⁺² chelates with phthalamates prevented steel from further corrosion.     

New thio-compounds as corrosion inhibitor for steel in 1 M HCl

Some S-containing compounds newly synthesised have been tested as inhibitors for the corrosion of steel in 1 M HCl solution. Weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods are used. The inhibiting action increases with the concentration of the compounds tested. The highest efficiency 95% is obtained at 10⁻⁴ M of [(11-hydroxyundecyl)thio]acetic acid (3 and 4). We note good agreement between gravimetric and electrochemical methods (potentiodynamic polarisation and EIS). Polarisation measurements show also that 3 and 4 act as mixed inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface happens with an activating mechanism. 3 adsorbs on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied between 308 K and 353 K.     

Benzimidazole and its derivatives as corrosion inhibitors for mild steel in 1M HCl solution

In this paper, the inhibition ability of benzimidazole and its derivatives against the corrosion of mild steel in 1M HCl solution was studied. The change of impedance parameters observed by variation of inhibitors concentration within the range of 50-250 ppm was an indication of their adsorption. The thermodynamic adsorption parameters proposed that these inhibitors retard both cathodic and anodic processes through physical adsorption and blocking the active corrosion sites. The adsorption of these compounds obeyed the Langmuir’s adsorption isotherm. The inhibition efficiency was increased with inhibitor concentration in the order of 2-mercaptobenzimidazole > 2-methylbenzimidazole > benzimidazole, which is in accordance with the variation of apparent activation energy of corrosion.     

An investigation of chloride-substituted Schiff bases as corrosion inhibitors for steel

Polarization and impedance measurements were performed on steel in deaerated 5% HCl solution with and without Schiff base additives within the concentration range 1 × 10⁻⁴–5 × 10⁻³ mol/dm³. The Schiff base compounds used were salicylaldimine, R, N-(2-chlorophenyl)salicyaldimine, 2Cl-R, N-(3-chlorophenyl)salicyaldimine, 3Cl-R, and N-(4-chlorophenyl)salicyaldimine, 4Cl-R. It was found that when the concentration of the inhibitors were increased the inhibitor efficiencies, η, also increased with increasing surface coverage. The results indicated that the ortho-substituted (2Cl-R) compound had the highest inhibition efficiency. All the Schiff base additives studied obeyed the Langmuir isotherm.     

A study of 4-carboxyphenylboronic acid as a corrosion inhibitor for steel in carbon dioxide containing environments

4-Carboxyphenylboronic acid (CPBA) has been found to be an efficient carbon dioxide (CO₂) corrosion inhibitor for steel in aqueous media. The results indicate that the addition of CPBA to CO₂ containing sodium chloride solutions at a low concentration is able to retard corrosion anodic reactions, reduce corrosion current densities, increase charge transfer and total resistances, resulting in more uniform and smoother steel surfaces. These effects are attributed to the formation of a barrier layer on steel surface, which provides metal surface protection. The inhibitor was also found to mitigate corrosion by promoting random distribution of minor anodes.     

A cationic gemini-surfactant as effective inhibitor for mild steel in HCl solutions

A cationic gemini-surfactant, namely 1,4-bis (1-chlorobenzyl-benzimidazolyl)-butane (CBB) was synthesized and its inhibition effect on the corrosion of mild steel in 0.5 M HCl solution was investigated by weight loss and electrochemical techniques. The results showed that CBB acts as an excellent corrosion inhibitor in 0.5 M HCl by suppressing simultaneously the cathodic and anodic processes via chemical adsorption on the surface of steel, which followed the Langmuir adsorption isotherm. The inhibition efficiency increased with the increase of CBB concentration and temperature. The adsorption mechanism of the compound was discussed in terms of thermodynamic and kinetic parameters deduced from the experimental data.     

电弧喷涂锌涂层的酸雨腐蚀性能

热镀锌涂层因具有优越的耐腐蚀性、涂装性能等被广泛应用于工业生产众多领域,成为金属材料在户外工作环境下防腐蚀的有效措施之一。为研究热喷涂锌涂层在酸雨中的腐蚀行为,采用电弧喷涂技术在Q235碳素结构钢表面喷涂锌涂层,模拟酸雨腐蚀环境,在腐蚀液pH值改变的情况下,采用SEM,XRD,硬度测试及失重分析等手段,分析不同pH值溶液腐蚀后涂层的表面形貌和腐蚀产物,及试样的硬度变化和腐蚀速率情况。结果表明,锌涂层的表面腐蚀会随着模拟酸雨溶液pH值的降低而加重,其表面腐蚀产物逐渐增多,腐蚀产物的形貌由小块状逐渐变成羽针状和岛状,主要成分为Zn(OH)2,ZnSO4和Zn4SO4(OH)6·3H2O;涂层表面硬度最高为23.4 HV、最小腐蚀速率为0.21×10-4g/(m2·h),但当模拟酸雨溶液pH值由7降至2.8时,涂层表面硬度降低约12%,腐蚀速率约增大至最小值的26倍;模拟酸雨溶液pH值在5～2.8时,溶液对锌涂层的腐蚀比较严重。     

A theoretical study of some hydroxamic acids as corrosion inhibitors for carbon steel

The corrosion inhibition characteristics of two hydroxamic acids, i.e., oxalyl-dihydroxamic acid (C2) and pimeloyl-1,5-di-hydroxamic acid (C7), on carbon steel has been studied using density functional theory (DFT). Quantum chemical parameters such as highest occupied molecular orbital energy (E_HOMO), lowest unoccupied molecular orbital energy (E_LUMO), and energy gap (ΔE) have been calculated using B3LYP/6-31 + G∗∗ basis set. The relationship between the inhibition efficiency and quantum chemical parameters has been discussed in order to elucidate the inhibition mechanism of these compounds.     

Experimental and theoretical study on the inhibition performance of triazole compounds for mild steel corrosion

A relationship between quantum chemical parameters for three triazole compounds and their inhibition ability was studied using electrochemical measurements (potentiodynamic polarization and EIS), molecular dynamic method and quantum chemical calculations. Electrochemical measurements results revealed that the inhibition efficiencies increased with the concentration of inhibitors. The molecular dynamic method results showed that the higher interaction potential between the inhibitor and metal surface, the higher the inhibition efficiency. The quantum chemical calculation results showed that the triazole ring is the active site in these inhibitors and they can absorb on Fe surface by donating electrons to Fe d-orbital.     

Thermodynamic, electrochemical and quantum chemical investigation of some Schiff bases as corrosion inhibitors for mild steel in hydrochloric acid solutions

The corrosion inhibition of mild steel in 1.0 M HCl solution by four Schiff bases was investigated using weight loss and electrochemical measurements and quantum chemical calculations. All compounds showed >90% inhibition efficiency at their optimum concentrations. The activation energy (E_a) of corrosion and other thermodynamic parameters were calculated to elaborate the mechanism of corrosion inhibition. The adsorption of the inhibitors on the mild steel surface follows Langmuir isotherm model. Polarization studies indicated that all studied inhibitors are mixed type. The computed quantum chemical properties viz., electron affinity (EA) and molecular band gap (ΔE_MBG) show good correlation with experimental inhibition efficiencies.     

Electrochemical and quantum chemical studies of some azomethine compounds as corrosion inhibitors for mild steel in 1 M hydrochloric acid

The corrosion inhibition effect of new azomethine compounds: PhNNC (COCH₃)NC₆H₄Y {Y = OCH₃ (SB₁), CH₃ (SB₂), H (SB₃), Br (SB₄) and Y = Cl (SB₅)} on mild steel in 1 M HCl, was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemistry analysis. It has been found that the inhibition efficiency increased with increasing inhibitor concentration. The polarization curves showed that these Schiff bases function as mixed inhibitors. The adsorption of studied compounds on mild steel surface was found to follow the Langmuir isotherm. Molecular modeling was used to correlate corrosion inhibition properties and calculated quantum chemical parameters.     

An investigation of benzimidazole derivative as corrosion inhibitor for mild steel in different concentration HCl solutions

The influences of a benzimidazole derivative, namely 1,8-bis (1-chlorobenzyl-benzimidazolyl) -octane (CBO) on the corrosion behaviour of mild steel in different concentration HCl solutions were studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements and SEM observations. The results showed that CBO acted as an excellent and a mixed-type inhibitor via strongly chemical adsorption onto mild steel surface to suppress simultaneously both anodic and cathodic processes according to the Langmuir adsorption isotherm. Inhibition efficiencies increased with increasing concentration of inhibitor and HCl. An inhibition mechanism was proposed in terms of strongly adsorption of inhibitor molecules on mild steel surface.     

冲压速度对DP780双相钢和304不锈钢胀形性能影响的试验对比分析

利用速度可控的小松伺服压力机对双相钢DP780与304不锈钢1 mm板料进行杯突试验,根据杯突试验值Er的大小来研究冲压速度对试验结果的影响。对比双相钢DP780及304不锈钢两种材料的试验结果发现,在冲压速度由3 mm·s-1增大到30 mm·s-1的过程中,304不锈钢杯突值从9.39 mm降低到8.59 mm,双相钢DP780杯突值从7.53 mm降低到7.39 mm。此实验结果使速度对材料拉胀成形性能的影响得到确认,即在3~30 mm·s-1区间内,随着冲压速度的升高,材料杯突值不断减小,材料的抗破裂成形性能逐渐降低,即材料的拉胀成形性能降低。     

Novel isoxazolium cationic Schiff base compounds as corrosion inhibitors for carbon steel in hydrochloric acid

The corrosion of carbon steel in 0.5 M HCl at 25 °C was investigated in the presence of two synthesized quaternary isoxazolium Schiff base series using gravimetric, polarization and electrochemical impedance measurements. The measurements showed a gradual increase in the inhibitors efficiencies by increasing the dose and hydrophobic chain length. The calculated activation energies proposed that the inhibitor molecules are adsorbed physically onto the metal surface. Surface activity-inhibition tendency relation showed the gradual increase of the inhibition efficiency by increasing the hydrophobic chain length.     

The effect of electrolyte flow on the performance of 12-aminododecanoic acid as a carbon steel corrosion inhibitor in CO2-saturated hydrochloric acid

The effect of flow and flow pattern of CO₂-saturated HCl on the corrosion inhibition of carbon steel (CS) by 12-aminododecanoic acid (AA) was investigated in a square duct, rotating disk electrode (RDE), and jet impingement cell configuration. 3 mM AA provided high corrosion inhibition efficiency in the square duct and RDE configuration. However, in 1 mM AA the inhibition efficiency decreased with an increase in Re, due to desorption of AA from the CS surface. AA was found to poorly protect CS in the impingement-jet configuration at low Re, while at high Re, acceleration of CS corrosion was recorded.     

Tryptamine as a corrosion inhibitor of mild steel in hydrochloric acid solution

The inhibitor effect of tryptamine on the corrosion of mild steel in 0.5 M hydrochloric acid at 30 °C was investigated using linear polarization, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiency increases with an increase in concentration of tryptamine. At 500 ppm tryptamine the inhibition efficiency calculated by these techniques is around 97%. Cathodic and anodic polarization curves of mild steel in the presence of different concentrations of tryptamine at 30 °C reveal that it is a mixed type inhibitor. Tryptamine follows Langmuir adsorption with adsorption free energy of −35.07 kJ mol⁻¹.