These deposits were formed early in the development of life on earth; when living things were mostly anaerobic bacteria, which fed on sulfur carbon dioxide and nitrogen. As the bacteria fed, they released oxygen as a waste product, which in turn reacted with dissolved iron salts in the seawater, to form insoluble iron oxides and hydroxides.
These settled to the bottom in vast quantities over millions of years; forming the basis of most of today's iron ore deposits. Military hardware and equipment in storage as War wastage reserves, tanks, missiles, ammunition, gearboxes, engines, even replacement parts and stores are highly susceptible to changes in humidity and consequently rusting and corrosion.
Storage of steel or metal products presents major problems where air is humid and there is a big variation in temperature during the 24 hours a day causing condensation at times. Inorganic : rust Organic : mold, mildew, fungus moisture causes corrosion.
Extends viability of stored parts and inventories Prevents failures Protects equipment when not in use Secures major facilities like power plants during lay-up. Brain dehumidifiers can maintain RH as low as 1% or even lower at a constant level, regardless of ambient conditions during production, processing, packaging and storage.
Spoilage due to mold, mildew and fungal decay of stored textiles, leather products, batteries, tires, stationery, food stuff, ration, etc., result due to condensation of moisture on stored material. Temperature fluctuations are responsible for wide range of humidity leading to condensation and for organic corrosion to set in.
Hygroscopic raw material storage requires humidity to be controlled between 35% to 40% RH as this prevents moisture regain and hence corrosion. Acids are chemical compounds with the ability to neutralize a base and a characteristic sour taste.
Being organic, a carbon atom must be present in its structure and being acidic its pH value always remains less than 7. Some simple forms of organic acids are less reactive to mineral acids which make them a great choice for the treatment or prevention of corrosion in several industries.
Furthermore, some other forms of organic acids like citrate and lactate are generally used as buffer solutions. Organic acids are more beneficial when used in their dissociated form as it makes them capable of cheating metal ions that tend to accelerate the removal of rust.
They are either acids or oxygenless and based on the number of hydrogen atoms they can be mono, DI, or Triassic. Organic Acid Inorganic Acidic is an organic compound with acidic properties. It is an inorganic compound with acidic properties. It contains carbon atoms, e.g. a carbon skeleton. Most of the inorganic acids lack the carbon atoms. Generally, they are weak acids. Generally, they are strong acids. Generally, it is insoluble in sometimes water miscible with water. Generally, It is soluble in water. It is soluble in organic solvents. It is insoluble in organic solvents. It has a biological origin. It does not have any biological origin. It accelerates the removal of rust by cheating metal ions. It is highly corrosive, reacts easily with metals and causes corrosion.
To play this quiz, please finish editing it. The word organic means something very different in chemistry than it does when you're talking about produce and food.
Note that containing carbon is not sufficient for a compound to be considered organic. These include nucleic acids, fats, sugars, proteins, enzymes, and hydrocarbon fuels.
Inorganic include salts, metals, substances made from single elements and any other compounds that don't contain carbon bonded to hydrogen. For example, when scientists talk about organic molecules discovered on Pluto, this doesn't mean there are aliens on the world.
But all of them are subjected to interactions with the environment what adversely affects the structural performance, including reliability over time. The deterioration process concerns all materials, not only metals but also plastics, glass, concrete, wood, leather and paper.
Corrosion of glass is due to reactions with atmospheric pollutants such as SO 2 or CO 2 as well as hydroxyl ions attack on Sloane bonds what leads to extraction of silica . The maintenance costs of concrete microbial corrosion (CMC) of sewer pipelines in Hamburg (Germany) in the 1970s reached up to €25 million whereas in Los Angeles (USA), the sewer pipe of 208 km in a total length of 1900 km had been damaged by CMC, and the rehabilitation costs were as high as $400 million .
Wood may also cleave or decompose what is related to its chemical structure based on cellulose, lignin and hemicelluloses. In natural environment, wood is rapidly colonized by microorganism and insects and the process of decomposition begins .
However, the environmental pollution, global warming and climate change are the direct cause for increasing corrosion costs. Chemical corrosion takes place in dry gases and nonconductive liquids where there is no current/electron flow.
The another part is cathode, where depolarization takes place, mainly reduction of oxygen and hydrogen cation . Microbes form a biofilm on the metal surface which is very good environment for their growth .
Another term associated with material’s degradation is erosion which means a progressive loss of original material from a solid surface due to mechanical interaction between the surface and a fluid, a multicomponent fluid or impinging liquid or solid particles . To estimate real corrosion damage, many direct and indirect physicochemical analytical methods are used .
However, many non-intrusive methods are commonly applied, like ultrasonic , potential measurements, radiography, eddy current, magnetic particle inspection and acoustic emission . Ultrasonic allows to control thickness by using sonic waves with high frequency (1–6 MHz).
The sound waves are produced from mechanical stress (pressure or temperature changes) so the technique does not need excitation or human intervention . This technique is a source of large amount of data which requires elaborate filtering and analysis .
Potential measurements to control corrosion can be done with a voltmeter with high internal resistance. Another method, radiography, uses ability of gamma radiation to penetrate the investigated material.
The gamma radiation can penetrate up to 5 cm of the metal with acceptable signal of attenuation . Eddy current is a technique used for monitoring of cracking and pitting corrosion of metallic materials.
The method depends on the eddy current produced in the surface of the metallic material. Another possibility to control corrosion is to measure indirect changes such as hydrogen evolution which is a product of cathodic reaction.
Water chemistry analyses can provide interesting information to corrosion monitoring program such as measurement of pH, conductivity or dissolved oxygen . However, the measurements are indirect which make it difficult to estimate real corrosion damage .
A sample of tested metal, previously carefully degreased and polished is weighed and immersed in an electrolyte solution for specified time (t). On the other hand, open circuit potential (OCP), named also corrosion potential (E corr), linear polarization resistance (LPR) and potentiodynamic measurements (Take slopes) are included in potentiometer methods .
After reaching an equilibrium, OCP (E corr), which is a difference in potential of micro cells of the metal, is registered. At that potential, oxidation and reduction reactions occur which allows estimating if the metal is resistant to corrosion in tested environment.
Graphical representation of results of the potentiodynamic measurements are Take slopes: graphs of applied potential (E, V) versus registered current density (i, A/cm 2) (Figure 2) . Analysis of obtained data consists in describing the studied system with an equivalent electrical circuit.
When the processes are related to charge transfer between metal and electrolyte, then the equivalent circuit consists in: solution resistance (R s), charge transfer resistance (R ct) and double layer capacitance (C DL) formed at the metal:solution interface. An example of the Nyquist diagram and the equivalent circuit is presented in Figure 3.
In practice, instead of double layer capacitance, constant phase element (CPE) is used. Surface morphology of the metal is examined by using microscope techniques, SEM, AFM or TEM.
Very often confocal laser scanning microscope (Clam) is used to choose the right area of the surface for further SEM/AFM/TEM examinations . Volumetric method measures volume of evolving gas in the corrosive reaction.
Magnetic-powder testing consists in irregularity of distribution of the magnetic field in material’s defects. There are five primary methods of corrosion control: (I) material selection, (II) design, (III) cathodic protection, (IV) coatings and (V) inhibitors.
Cathodic protection is an electrical method to reduce corrosion rate of metallic structures in electrolytes such as soil or water . Corrosion control by anoxic protection is known from the literature but currently it is rarely used due to high restrictions.
Inhibitors are adsorbed on the surface of the metal and form a protective thin film . Inorganic corrosion inhibitors, besides the oldest one, that is, molybdate anion, belong to calcium nitrite, rare earth metals salts, zinc phosphate, chromates and lanthanide compounds.
The corrosion inhibitors can be introduced as protective coating , bio-based lubricants and smart coatings that are released by the action of specific stimulus (e.g. change of pH, ionic strength or the change of electrode potential) . Organic corrosion inhibitors are widely used in industry because of their effectiveness at wide range of temperatures, compatibility with protected materials, good solubility and relatively low toxicity This is a very important issue for researchers which is confirmed by an increasing number of papers (Figure 4).
It is very important to use the right amount of an anode inhibitor, because insufficient concentration to cover all the active sites can lead to localized corrosion which is difficult to detect. Mixed inhibitors provide the highest protection because they affect both cathodic and anoxic reactions.
Number of published papers about organic corrosion inhibitors versus year of publication. Chemical adsorption is connected with the donor-acceptor interactions between free electron pairs and vacant, low energy d-orbital of metal (Figure 5).
Schematic diagram representing the adsorption mechanism of Shift bases on mild steel surface . Effective organic corrosion inhibitors should contain hetero atoms (nitrogen, oxygen, sulfur and phosphorus) with lone electron pairs and moiety with electrons (aromatic rings and multiple bonds) that can interact with free orbital d metal, favoring the adsorption process .
Also, the standard enthalpy of adsorption provides valuable information about the mechanism of corrosion inhibition. Presence of the hetero atoms with lone pair of electrons like nitrogen, oxygen, sulfur or phosphor as well electrons of multiple bonds or aromatic rings enhance adsorption phenomena .
Chemisorption involves transfer or sharing of unbounded electrons between the inhibitor molecule and the metal surface . In acid environment, hetero atoms are pronated that additionally promotes the interactions between the inhibitor and the surface.
The adsorption of organic corrosion inhibitors onto the surface of a corroding metal may be regarded as a substitution process between the organic compound, especially Asiatic chain in aqueous phase and water molecules adsorbed on the metal surface: Where Org (sol) and Org (ads) are, respectively, the organic species dissolved in the aqueous solution and adsorbed onto the metallic surface; H 2 O (ads) and H 2 O (sol) is the water molecule adsorbed onto the metallic surface and that in the bulk solution; x is the size ratio representing the number of water molecules replaced by one organic adsorb ate.
The Asiatic chain has an influence on the corrosion protection due to the repulsion of nonpolar hydrophobic part of inhibitor and polar medium. The size and molecular weight of organic inhibitor also have an impact on the efficiency of inhibition .
The large number of organic corrosion inhibitors can be divided for some clusters with specific elements, like (Figure 6): Nitrogen, sulfur, oxygen and clusters of organic corrosion inhibitors.
Data about material, kind of inhibitor and inhibition efficiency are summarized in Table 1. This involves the ability to interact with many, so that surface adsorption is stronger in comparison with monomers.
For example, deoxyribonucleic acid is a bio polymer with high inhibition efficiency against steel reinforcement . Similarly, natural polymer, chitosan, is used as corrosion inhibitor of copper in hydrochloric acid .
Due to the presence of positively charged nitrogen atom and the amphipathic structure, quaternary ammonium salts are the center of interest for using them as highly effective corrosion inhibitors . The neutral charge of the molecule is retained by the presence of organic or inorganic anions.
Gemini's surfactants also have a larger molecular area in comparison to monomer analogs which cause them to act more efficiently as corrosion inhibitors . Inhibition efficiency (IEC) is affected not only by number of positively charged nitrogen atoms but also depends on the length of alkyl chain.
Additional hetero atoms or electrons also favor adsorption onto the metal surface . Influence of the presence of hetero atoms and electrons on inhibition efficiency of steel in 1 M HCl.
Structure of the Gemini surfactants and Nyquist plots for stainless steel in 3 M HCl in the presence and absence of the synthesized inhibitors (naturally aerated, 7 days of immersion). The stainless steel impedance response in the blank solution (black) shows a smaller diameter compared to the diameters of the plots for both Gemini surfactants, the latter indicating higher resistance, that is, lower corrosion rate.
Some of Gemini surfactants, which are already commercially used, are a part of special compositions which are based on synergistic effect in order to lower the concentrations used . Some Gemini surfactants are a part of patent about multifunctional corrosion inhibitors for iron alloys (tanks transporting oil and liquid fuel) which are subjected to acidic pollution, sulfur compounds, water, oxygen as well as calcium and magnesium cations .
Another patent is about using Gemini surfactants as corrosion inhibitors of metallic materials which are used for gas and oil extraction . One of the interesting organic corrosion inhibitors are ionic liquids (ILS) as potentially green chemicals.
The corrosion inhibition of the prepared polymeric ionic liquid on steel in acidic medium was investigated by using different electrochemical techniques . Biocorosion is mostly a result of the interaction of mechanical, physical, chemical and/or biological factors.
Wind, water, particles of dust, pollution atmosphere and water, and, in the case of stone materials, action light and temperature changes cause damage to materials, allowing penetration moisture and colonization of microorganisms on their surface. Biofilm creates very good environment for growing microorganism, and increase rate of corrosion even to 10,000 times.
The kinetics of bio corrosion is strongly influenced by the concentration of oxygen, presence of salts, pH value, redox potential and conductivity. The living bacteria produce extracellular polymeric substances (EPS) and form biofilms on the metal surface.
The most common methods to observe bio corrosion effects are scanning electron microscope (SEM) and confocal laser scanning microscope (Clam) as well as X-ray photo electron spectroscopy and time of flight-secondary ion mass spectroscopy (Tonsils) . In a sense, these organisms “breathe” sulfate rather than oxygen in a form of anaerobic respiration .
Methods to significantly slow have concern on inhibition of the growth of microorganisms and modification of the environment in which the corrosion process takes place. The basic steps to prevent and control bio corrosion are (i) cleaning procedures; (ii) microbiomes; (iii) coatings and (iv) cathodic protection .
Social activities of the synthesized surfactants were achieved by dropping the redox potential and confirmed preventing sulfide production in the reactor’s bulk phase. This means that all sulfidogenic bacteria are active in the reactor’s bulk phase and on the metal surface.
SABENA et al. describe potential bio corrosion inhibitors that contain quaternary ammonium atom (Figure 11) . Quite new approach is using surface modification technologies such as short anti-biofilm peptides applying by immobilization method also using small dipeptides .
Using of coatings based on silicone and epoxy resins are also method to protection against bio corrosion. Quantum chemical methods are useful for designing new, effective organic corrosion inhibitors as they relate electron structure of the compounds to their reactivity.
Every year density functional theory (DFT) is more often applied for predicting a theoretical ability to inhibit corrosion process according to some quantum chemical parameters: energy of the highest occupied molecular orbital (E HOMO), energy of the lowest unoccupied molecular orbital (E Lump), gap energy (He), chemical hardness (), softness (), ionization potential (I P) and electron affinity (E A), electronegativity () and fraction of electron transferred (In) . The energy of the lowest unoccupied molecular orbital (Lump) is related to the ability to accept electrons from the metal.
The dipole moment () is also an important parameter which gives information about polarity in a bond. Corrosion inhibition efficiency increases with increasing the value of , due to the stronger dipole-dipole interactions with the metal surface which results in stronger adsorption and efficient corrosion inhibition .
High value of suggests strong ability to attract electrons from the metal which leads to greater interactions and higher corrosion protection. Some quantum parameters for Gemini surfactants and corrosion inhibition efficiency (IEC) of carbon steel are presented in Table 5 .
According to the presented results, elongating the alkyl chain (R) leads to increasing corrosion inhibition efficiency from 79.86 to 81.32%. Based on the electron parameters, all values of E Lump are negative, which are associated with physisorption.
The values of In which are higher than 0 indicate that electrons are transferred from inhibitor to free d orbital of the metal. The reviewed literature data clearly indicate that a new way to inhibit deterioration processes can be multifunctional Gemini surfactants.
Gemini alkylammonium surfactants with the highest corrosion inhibition efficacy can be synthesized according to prediction by theoretical calculations structures.