Level Of Corrosion Protection Research Articles

Physical scale modelling of stray current interference to shipboard ICCP system

ABSTRACTCathodic protection is commonly used for corrosion protection of the underwater hull structures of naval platforms. Cathodic protection works by establishing an electrostatic field that provides the desired potential and current distributions in the seawater surrounding the structures to be protected. Interference to a ship’s cathodic protection system may occur when the ship is alongside a jetty or another naval ship due to the influence of the electrostatic field associated with the cathodic protection system employed on the jetty or another naval ship. The interference may alter the electrostatic field surrounding the ship and, therefore, the level of corrosion protection to the ship hull. In the current study, a physical scale modelling technique is used to evaluate how, and to what extent, the level of cathodic protection on a ship hull could be affected by an external current source. A 1/100 scale ship model with two-zone four-anode impressed current cathodic protection (ICCP) system is used in the study. The modelling results indicate that the presence of stray current may affect the potential distribution along the ship hull. The extent of stray current effect depends on a number of factors including the relative position and layout of stray current source, the magnitude and direction of the stray current flow and the operating mode of the shipboard ICCP system.

Laboratory and field testing of bolting systems subjected to highly corrosive environments

The capacity of ground support components which have been affected by corrosion is reduced and may ultimately lead to dynamic failure of the component and the strata. In order to maintain an effective, long-term ground support system, significant campaigns of rehabilitation are often required in corrosion affected areas which also expose the workers to hazardous conditions. The most common corrosion protection for steel ground support utilises sacrificial systems such as galvanising. Galvanising has previously been proven to be susceptible to some corrosion processes. Stainless steel is the most effective in resistance to corrosion, but can be cost prohibitive, and its mechanical properties often make it unsuited to use in ground support components. Providing an outer protective plastic coating to bolts has proven to be an effective means of protecting the inner steel bar from corrosion. However, these support systems tend to be susceptible to coating damage, and require post cement grouting to provide full encapsulation. In comparison to a standard bolt/resin system, they can be slow to install and expensive. These systems have also been shown to reduce overall load transfer performance of the bolting system. In order to provide a higher level of corrosion protection whilst maintaining current installation practices and bolting cycle times, Minova has developed the Enduro™ steel ground support range. The Enduro™ range consists of standard Minova steel ground support components which have been treated with a unique coating process. The Enduro™ coating has been tested in the harshest of conditions, in laboratory controlled conditions and in underground trials. It has been proven to effectively resist or completely eliminate the formation of corrosion, even in the most aggressive environments. This paper explains the process and provides the details of the laboratory and underground corrosion performance testing carried out on Enduro™ ground support products.

Fundamental Investigation of E-Coat Systems for Next Generation Corrosion Control

Electrodeposition of coatings is widely used in the auto industry to protect against corrosion. Increased fundamental understanding is needed to enhance the effectiveness of coatings while decreasing the environmental risks associated with surface treatments and coatings, as well as the processes used to form them. In addition, the incorporation of fundamental understanding into modeling tools will help to improve the quality of predictions and ensure that the desired level of corrosion protection is achieved. Fundamentally based models can also provide insight to guide the development and use of new types of environmentally friendly surface pretreatments. Key parameters of interest to the present study include the coulombic efficiency (mass deposited per charge), the coating resistivity, bath conductivity, the degree of neutralization and the extent of amine substitution. The influence of operating conditions such as temperature and flow on these parameters is also critical. In this study, experiments are performed to investigate the influence of factors such as the degree of neutralization and the extent of amine substitution on the size of resin particles in solution and on the processes that render the resin insoluble, leading to deposition. Models are used to describe and quantify critical mechanisms. The impact of key parameters on the local deposition rate and on the coulombic efficiency is demonstrated. The ability to determine the local deposition rate is critical to the performance of large-scale systems and to our ability to predict that performance for a variety of bath compositions, operating conditions, and surface pretreatments.

In situ evaluation of corrosion damage using non-destructive electrochemical measurements—A case study

Field application of electrochemical measurements with a non-invasive electrode arrangement has been used for investigating corrosion damage and protectiveness of a paint coating on an artwork sculpture. For this field application solid state probes were designed and used in electrochemical impedance spectroscopy (EIS) and electrochemical noise measurement (ENM) to evaluate the level of corrosion protection afforded by the paint coating. Samples were also analyzed in laboratory using analytical techniques. Results of electrochemical measurements indicated poor protective properties of the paint coating while analytical examinations revealed an inhomogeneous structure of the coating and a highly porous structure of the oxide scale.

Improved corrosion protection of magnesium by hydrothermally deposited biodegradable calcium phosphate coating

The corrosion protection of hydrothermally deposited calcium phosphate coatings on AZ31 magnesium alloy were studied for their potential use in biocompatible and bioresorbable temporary implants. The coatings mainly consisted of calcium phosphate phases (monetite and tricalcium phosphate). Potentiodynamic and electrochemical impedance spectroscopy (EIS) confirmed that the coatings provided varying levels of corrosion protection depending on the coating deposition temperature and duration. EIS results showed that the size of capacitance loops and the absolute impedance value (|Z|) increases by increasing the deposition temperature and corresponding growth in coating thickness. In agreement with the electrochemical experiments, immersion tests in simulated body fluid also indicated large improvement in corrosion protection as the mass loss was significantly reduced when coating was applied as compared to the bare metal. Using the thickest coating obtained at 190 °C deposition temperature, the corrosion current density of the coated magnesium was 10,000 fold lower compared to the bare metal. This result confirmed that the new hydrothermal coating is suitable to protect Mg implant against corrosion with further advantage of being bioactive and biodegradable.

Control the Corrosion of Magnesium for Implant Application By Hydrothermally Deposited Biodegradable Calcium Phosphate Coating

The corrosion protection of hydrothermally deposited calcium phosphate coatings on AZ31 magnesium alloy was studied in simulated body fluid (SBF) solution for their potential use as biodegradable implants. The coating mainly consisted of bioresorbable monetite phases. Potentiodynamic and electrochemical impedance spectroscopy (EIS) confirmed that the coatings provided varying levels of corrosion protection depending on the coating deposition temperature. By increasing the deposition temperature and corresponding growth in coating thickness the corrosion current density of the coated magnesium was 10,000 fold lower compared to the bare metal; indicating significantly enhanced corrosion performance of Mg substrate, reaching the corrosion protection requirement for magnesium implant. The barrier effect of Ca-P layers was further supported by the observed magnitude of anodic and cathodic Tafel slopes. Coated samples displayed much larger slopes than bare Mg substrate. EIS results showed that the size of capacitance loops and the absolute impedance value (|Z|) increases. By increasing the deposition time the corrosion mechanism was changed as a result of partial delamination of top surface of coating. In agreement with the electrochemical experiments, immersion tests in SBF also indicated large improvement in corrosion protection as the mass loss was reduced almost three times when coating was applied as compared to the bare metal. The uncoated Mg substrate undergoes severe and non-uniform corrosion after 28 days immersion in SBF solution; while, the coated samples displayed intact coating and no obvious pits were observed on the coating surface. The described biocompatible and biodegradable coatings significantly improved corrosion resistance of Mg substrate and can be promising candidate for biomedical application. Keywords: Magnesium, Calcium-Phosphate coating, Corrosion resistance, EIS

An investigation of the typical corrosion parameters used to test polymer electrolyte fuel cell bipolar plate coatings, with titanium nitride coated stainless steel as a case study

Stainless steel bipolar plates (BPP) for polymer electrolyte membrane fuel cells (PEMFCs) have good manufacturability, durability and low costs, but inadequate corrosion resistance and elevated interfacial contact resistance (ICR) in the fuel cell environment. Thin film coatings of titanium nitride (TiN) of 1 μm in thickness, were deposited by means of physical vapour deposition (PVD) process on to stainless steel (SS) 316L substrates and were evaluated, in a series of tests, for their level of corrosion protection and ICR. In the ex-situ corrosion tests, variables such as applied potential, experimental duration and pH of the sulphate electrolyte at 80 °C were altered. The ICR values were found to increase after exposure to greater applied potentials and electrolytes of a higher pH. In terms of experimental duration, the ICR increased most rapidly at the beginning of each experiment. It was also found that the oxidation of TiN was accelerated after exposure to electrolytes of a higher pH. When coated BPPs were incorporated into an accelerated fuel cell test, the degradation of the fuel cell cathode resembled the plates that were tested at the highest anodic potential (1.4 VSHE).

Steel surface preparation prior to painting and its impact on protective performance of organic coating

The influence of surface preparation on performance of alkyd coatings on steel was investigated. Degreasing, abrasion with emery, acid pickling, hydroblasting and wet abrasive blasting methods were used to modify the surface of steel before painting. Steel surfaces were analytically and morphologically characterized before painting. DC resistance and pull-off adhesion methods were used to evaluate the performance of alkyd coatings on differently prepared surfaces. Results implied the key role of oxide layer in maintaining the high level of corrosion protection. Also the detrimental influence of the inherent contamination caused by wet abrasive blasting method was shown as a cause of early failure of protective properties. Comparison between electrochemical and adhesion results showed that they may not indicate towards similar directions in terms of protective properties which is due to the different factors affecting them.

Control of the Corrosion of Magnesium for Implant Application by Hydrothermally Deposited Biodegradable Calcium Phosphate Coating

The corrosion protection of hydrothermally deposited calcium phosphate coatings on AZ31 magnesium alloy was studied in simulated body fluid (SBF) solution for their potential use as biodegradable implants. The coating mainly consisted of bioresorbable monetite phases. Potentiodynamic and electrochemical impedance spectroscopy (EIS) confirmed that the coatings provided varying levels of corrosion protection depending on the coating deposition temperature. By increasing the deposition temperature and corresponding growth in coating thickness the corrosion current density of the coated magnesium was 10,000 fold lower compared to the bare metal; indicating significantly enhanced corrosion performance of Mg substrate, reaching the corrosion protection requirement for magnesium implant. The barrier effect of Ca-P layers was further supported by the observed magnitude of anodic and cathodic Tafel slopes. Coated samples displayed much larger slopes than bare Mg substrate.EIS results showed that the size of capacitance loops and the absolute impedance value (|Z|) increases. By increasing the deposition time the corrosion mechanism was changed as a result of partial delamination of top surface of coating. In agreement with the electrochemical experiments, immersion tests in SBF also indicated large improvement in corrosion protection as the mass loss was reduced almost three times when coating was applied as compared to the bare metal. The uncoated Mg substrate undergoes severe and non-uniform corrosion after 28 days immersion in SBF solution; while, the coated samples displayed intact coating and no obvious pits were observed on the coating surface.The described biocompatible and biodegradable coatings significantly improved corrosion resistance of Mg substrate and can be promising candidate for biomedical application.

Anticorrosion Properties of the Extract of Rapeseed Oil Cake as a Volatile Inhibitor of the Atmospheric Corrosion of Steel

We study the composition of the volatile fractions of the isopropanol extract of rapeseed (Brassicaceae family) oil cake by the chromatography-and-mass spectrometry method. It is shown that their main ingredients are glycosides, ketones, aldehydes, saturated and unsaturated fat acids, and steroids. It was discovered that the extract provides a high level of corrosion protection of the metal as a volatile corrosion inhibitor under the conditions of periodic condensation of moisture. It is demonstrated that the corrosion rate of steel decreases as its concentration increases, and the process of formation of films from the vapor phase has a long-term character. The film formed on the surface of steel from the gas–vapor phase of the extract gives an aftereffect on a level of 90% under the conditions of periodic moisture condensation for 504 h.

Effect of pH and carbon nanotube content on the corrosion behavior of electrophoretically deposited chitosan–hydroxyapatite–carbon nanotube composite coatings

In the first stage, chitosan (CH)–hydroxyapatite (HA)-multiwalled carbon nanotube (MWCNT) composite coatings were synthesized by electrophoretic deposition technique (EPD) on 316L stainless steel substrates at different levels of pH and characterized by X-ray diffraction (XRD), Raman spectroscopy, FTIR and field emission scanning electron microscopy (FESEM). A smooth distribution of HA and MWCNT particles in a chitosan matrix with strong interfacial bonding was obtained. In the next stage, effects of pH and MWCNT content of the suspension on the corrosion behavior and deposition mechanism were studied. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) curves revealed that increasing pH level of the suspension increases the corrosion protection properties of the deposited composite coating in simulated body fluid (SBF). Furthermore, Nyquist plots showed that increasing MWCNT content of the suspension resulted in higher amounts of Rp, but because of the capillary properties of MWCNTs and degradability of the chitosan matrix, corrosion protection level of the coatings containing HA–CH–MWCNT was lower than those of coatings containing solely HA–CH. Amperometric curves in different pH levels of the suspension revealed that the system is diffusion controlled at elevated pH values.

Transient Formation of Chromate in Trivalent Chromium Process (TCP) Coatings on AA2024 as Probed by Raman Spectroscopy

We report evidence for the transient formation of Cr(VI) oxide species in the Trivalent Chrome Process (TCP) coating on AA2024-T3 alloys. TCP is the leading replacement coating for the environmentally-unfriendly chromate conversion coating (CCC) that is commonly used to pretreat aerospace aluminum alloys. Transient formation of hexavalent chrome in these coatings is important to learn about as the presence of this species will affect the active level of corrosion protection as well as the environmental impact of the coating. Specifically, we tested the hypothesis that dissolved O2 is reduced to H2O2 at the Cu-rich intermetallic sites and that H2O2 diffuses to nearby sites in the coating to oxidize native Cr(III) oxide (Cr(OH)3 or Cr2O3) to Cr(VI) oxide (CrO42−). Raman microprobe spectroscopy was used to spatially distinguish between the two species based on the different vibrational modes of Cr(III)-O (520–580 cm−1) and Cr(VI)-O (840–904 cm−1). Results are presented that support a mechanism whereby the formation of Cr(VI) oxide species is linked to the production of H2O2 locally within the coating. The H2O2 is presumed to arise from the 2e− reduction of dissolved O2 at Cu-rich intermetallic sites. A variety of Cr(VI) oxides and mixed oxides are formed in the coating during full immersion testing in air-saturated electrolyte solutions or aging in air.

The corrosion protection system used at OOO Gazprom Transgas Yekaterinburg

The work of the corrosion protection system used at OOO Gazprom Transgas Yekaterinburg is considered, mainly for the period of 2008. It is noted that the passive corrosion protection component, which consists of different pipeline wrappings, requires repair and replacement. The active (electrochemical) corrosion protection component achieves a high level of corrosion protection of gas pipelines via the application of different technical processes. Their work is exemplified by the main gas pipelines of the Nev’yansk Regional Gas Pipeline Operation Center.

From Food Preservation to Surface Protection: Enhanced Corrosion Protection by Fatty Acid Salts

AbstractThe ability of dissolved monocarboxylate salts, often used as food preservatives, to produce surface passivation and to inhibit aqueous corrosion of metals and alloys is discussed. Electrochemical measurements indicate that the inhibiting efficiency of these compounds, with a general formula Cn‐1H2n‐1COOK or CnK (n = 3…12), is dependent on the hydrocarbon chain length. Inhibiting efficiency was higher for a longer hydrocarbon chain of n‐alkanoic acid. Copper corrosion protection level was found to increase with an increase in fatty acid salt concentration; the optimum concentration of potassium dodecanoate (C12K) in sulfate solutions was found to be 70 mM. Protective layers formed at the copper surface subsequent to exposure in various n‐alkanoate solutions were characterized by an electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared reflection spectroscopy, and contact angle measurements. Observed copper passivation is attributed to the growth of a protective film on the copper surface, containing both copper oxides and copper carboxylate compounds. The organic molecules enhance copper protection by covering copper oxides with a thin and dense organic layer, which prevents water molecules or aggressive anions from interacting with the copper surface.

Designing nanoprecipitation strengthened UHS stainless steels combining genetic algorithms and thermodynamics

A computational method for the design of precipitation hardened stainless steel is presented which combines genetic algorithms and thermodynamic computations. The aim of the algorithm is finding compositional scenarios for stainless steels displaying yield strength values exceeding those of their existing commercial counterparts. Strengthening results from ensuring the presence of fine lath martensite and a variety of nanoprecipitates. Using no less than 13 alloying elements, constrained by realistic minimum and maximum levels, the model leads to the design of four alloys for which strengthening is the result of either MC carbides, Cu, Ni rich intermetallics, or a combination of all of them. The model predictions are also compared to a variety of existing commercial high-end engineering steels, showing that the design strategy presented here may potentially lead to significant improvements in strength, while at the same time keeping the Cr level in the matrix above the critical corrosion protection level of 12 wt%.

Application of electrochemical noise to evaluate outdoor atmospheric corrosion of copper after relatively short exposure periods

This study focused on the application of electrochemical noise to assess the protection level of corrosion products formed on copper during relatively short exposure time in different outdoor atmospheres. Electrochemical noise, cathodic reduction measurements and gravimetric (mass loss) analysis were applied to copper samples exposed at urban and rural/industrial areas in Cuba for 4 months. Measurements of Electrochemical current noise indicated that the poorest protective corrosion products were formed on samples exposed to atmospheres with high concentration of H2S which agreed with the corrosion rate determined by mass loss and electrochemical chronopotentiometry (cathodic reduction). The electrochemical noise methodology proposed in this work showed acceptable and reproducible results by using an electrochemical cell in which the electrolyte was formed by a distilled-water wetted cloth in contact with the compounds present on a corroded metallic surface. This methodology indicated that the corrosion protection level of the corrosion products formed on copper is related to the corrosivity of the atmosphere.

Environmental friendly plasma electrolytic oxidation of AM60 magnesium alloy and its corrosion resistance

Plasma electrolytic oxidation of Mg-based AM60 alloys was investigated using 50 Hz AC anodizing technique in an alkaline borate solution, which contained a new kind of organic. The anodic film is relatively smooth with some micro pores and cracks, while the anodic film consists of MgO, MgAl 2O 4 and MgSiO 3. The electrochemical behavior of anodic film was studied by electrochemical impedance spectroscopy and potentiodynamic polarization. Polarization results indicate the PEO treatment can decrease corrosion current by 3–4 magnitude compared with blank AM60 alloy. The anodic film presents a good level of corrosion protection for AM60 magnesium alloy, over 272 h of the salt spray test based on ASTM B117. The effect of micro-structure and composition on corrosion protection efficiency was also investigated.

Coolants at Elevated Temperatures

Abstract Over the years, new performance requirements and environmental regulations have driven engine manufacturers to design new engines. The new engine technologies have resulted in different operating conditions in cooling systems. In general, a trend towards higher coolant temperatures is observed, which is expected to have an implication on the coolant stability and corresponding lifetime. In heavy duty applications, this trend is even more pronounced as engines are running longer and under more severe conditions. In this paper, a selection of different current coolant technologies available in the market have been tested to obtain more information on the influence of the coolant additive package on the thermal stability of the most commonly used coolant base fluid, mono ethylene glycol (MEG). For this reason glycol oxidation products have been measured after subjecting the coolants to high temperature oxidative conditions. In addition the physical/chemical stability of the coolants and corrosion protection level of the additive packages have been evaluated.

Corrosion inhibitor doped protein films for protection of metallic surfaces: appraisal and extension of previous investigations by Brenner, Riddell and Seegmiller

An evaluation of the efficacy of chromated protein coatings, originally proposed by Brenner, Riddell and Seegmiller has been undertaken. Some of their original application methods and coating solution formulations have been utilised to produce films on zinc electroplated steel surfaces. Subsequent morphological and corrosion studies have highlighted the enhanced corrosion resistance afforded by these treatments, attributed to the high level of hexavalent chromium dispersed in the coatings. Additional experiments were undertaken with molybdate, tungstate and cerium trichloride corrosion inhibitors as more environmentally friendly substitutes for the chromate. Although their performance was inferior, cerium trichloride did engender a promising level of corrosion protection to the electroplated zinc surfaces.

Plasma electrolytic oxidation of AM60 magnesium alloy: Monitoring by acoustic emission technique. Electrochemical properties of coatings

Magnesium alloy AM60 (6% Al) behaviour during Plasma Electrolytic Oxidation (PEO) was monitored by the Acoustic Emission (AE) technique. The process is divided into four stages, each one emitting characteristic acoustic signals. The following physical phenomena could be distinguished: bubbles during the conventional anodising step (stage 1), two discharge regimes, named microarc (stage 2) and arcing (stage 3) and film relaxation phenomena combined with bubbles coalescence inside the porous film after the anodising was stopped (stage 4). The applied DC current density has no visible effect on AE signals. The electrochemical behaviour of anodised samples has been investigated by electrochemical techniques. The anodic film provides a good level of corrosion protection only for a limited period of time. This lack of corrosion protection efficiency is due to the porous and non-perfectly adherent structure of the film.