Moving Forward Every Day — 2010.01.3

The reference answer provided by this site is: Hydrochloric acid is a strong reducing acid, and it is also one of the most corrosive substances. The standard potentials of most metals are below that of hydrogen; therefore, when in contact with hydrochloric acid solutions containing a high concentration of hydrogen ions, metal ions rapidly enter the solution while hydrogen ions are released as hydrogen gas, resulting in severe hydrogen evolution corrosion. Only some precious metals such as tantalum, platinum, gold, and silver, as well as a few alloys like nickel-molybdenum-iron alloy (Hastelloy B) and molybdenum-containing high-silicon iron, exhibit good corrosion resistance to hydrochloric acid.

【Physical and Chemical Properties】 Main component: HCl; Content: 36% for industrial grade. 　　Appearance and properties: Colorless or slightly yellow volatile liquid with a pungent odor. 　　pH:

Hydrochloric acid, with the chemical formula HCl, is an aqueous solution of hydrogen chloride. Its appearance and properties are those of a colorless or slightly yellowish, volatile liquid with a pungent odor. Concentrated hydrochloric acid is highly volatile and corrosive; high concentrations can cause severe harm to the human body. It has a pungent odor and can react with many metals. It is one of the three strong acids; when combined with nitric acid in a 3:1 ratio, it forms aqua regia, which can dissolve gold. Hydrochloric acid can react with certain active metal powders to release hydrogen gas. It can produce highly toxic hydrogen cyanide gas when in contact with cyanides. It undergoes a neutralization reaction with alkalis, releasing a large amount of heat. It is highly corrosive. It is highly acidic; it reacts with bases to produce chlorides and water. It can react with most carbonates to yield carbon dioxide and water. It reacts with active metal elements to produce hydrogen gas. It also reacts with metal oxides to form salts and water. Hydrochloric acid is a strong acid that possesses all the characteristics of acids, such as the ability to neutralize bases to produce salts and water ； Can dissolve basic oxides ； It can dissolve carbonates and release carbon dioxide gas ； It can dissolve relatively reactive metals (such as zinc, magnesium, iron), producing hydrogen gas. Concentrated hydrochloric acid can dissolve the less reactive metal copper. Storage: Due to the high volatility of hydrochloric acid, the hydrogen chloride that evaporates from it combines with water vapor in the air to form small droplets of hydrochloric acid, which then disperse in the air. Therefore, hydrochloric acid must be stored in a sealed container; otherwise, over time its quality will gradually decline as will its concentration. Concentrated hydrochloric acid evaporates very easily in the air, and it is highly corrosive to skin and clothing. Therefore, special care must be taken when using it! Its corrosiveness stems from the oxidizing property of hydrogen ions, and the degree of oxidizing power is related to the concentration of hydrogen ions. Using the concept of limits, there is only one molecule of HCl in 1 liter of water; it’s possible that they won’t react with each other even after half a day. But if there is 1 mole of HCl, the reaction will occur easily. By diluting with water to reduce the concentration, the corrosivity is diminished. It cannot corrode pure copper; titanium and MONEL alloys can resist corrosion, while Hastelloy performs well in the presence of hydrochloric acid. Concentrated sulfuric acid has dehydrating properties, while neither dilute hydrochloric acid nor concentrated hydrochloric acid possesses such properties; therefore, hydrochloric acid cannot cause wood to turn black. Nitric acid, sulfuric acid, hydrochloric acid – Corrosivity ranking: sulfuric acid, nitric acid, hydrochloric acid. In terms of acidity, sulfuric acid is stronger than hydrochloric acid, which is in turn stronger than nitric acid. In terms of oxidizing power, concentrated nitric acid is stronger than concentrated sulfuric acid, which is stronger than hydrochloric acid. However, concentrated sulfuric acid also has dehydrating properties

Hydrochloric acid is a strongly reducing acid and one of the most corrosive substances. The standard potentials of most metals are below that of hydrogen; therefore, when in contact with hydrochloric acid solutions containing a high concentration of hydrogen ions, metal ions rapidly enter the solution while hydrogen ions are released as hydrogen gas, resulting in severe hydrogen evolution corrosion.

⑴Pure nickel (alloy 200) exhibits excellent corrosion resistance to a wide range of reducing acids and salts, but it is not suitable for use in strongly oxidizing environments such as nitric acid. The most notable characteristic of pure nickel is its resistance to corrosion by strong alkalis, especially when these alkalis are in a molten state. Although it exhibits excellent corrosion resistance in dry halogen environments, nickel is not suitable for use in environments below the water dew point. For use in environments above 6000F, it is best to choose a low-carbon grade, designated as Nickel 201 (UNS N02201). ⑵ Nickel-copper alloy 400 has the same corrosion resistance as nickel; it is best used under reducing conditions, but it can also be damaged by oxidizing atmospheres. Alloy 400 exhibits excellent resistance to corrosion by halic acids and halogen compounds, and is particularly resistant to corrosion by hydrofluoric acid and high-temperature gases rich in fluorine or hydrogen fluoride. This alloy is widely used in treating sulfuric acid solutions, seawater, and brine. For applications that require higher strength, such as those for valve and pump components, alloy K-500 (N 05500) is often used; it is a precipitation-hardening variant of alloy 400. ⑶Nickel-chromium-iron alloy 600 features chromium added to the nickel matrix, which enhances the alloy’s resistance in oxidizing environments. Its corrosion resistance to inorganic acids is only moderate, but it has very good resistance to organic acids; therefore, it is widely used in the processing of fatty acids. It is also extensively utilized in the processing and production of strongly alkaline chemicals. Alloy 600 is also considered an excellent material for high-temperature applications where both heat resistance and corrosion resistance are required. Its excellent performance in high-temperature halogen environments makes it the best material choice for the processing of organic chlorides. In other high-temperature degradation processes, alloy 600 has been shown to possess excellent oxidation resistance, as well as resistance to carburization and nitridation. ⑷Nickel-chromium-molybdenum alloy 625, which incorporates molybdenum into nickel-chromium alloys, enhances resistance to corrosion by oxidative and reductive inorganic acids and salts. The addition of nickel makes the alloy susceptible to pitting and crevice corrosion caused by moist chlorides. Alloy 625 is a material with excellent fatigue resistance. Alloy 625LCF is a modified version of 625 that possesses the properties required for bellows; its advantage lies in its superior resistance to low-cycle fatigue and thermal fatigue. Like alloy 600, 625 can be effectively used as a heat-resistant and corrosion-resistant material. Its excellent high-temperature strength, as well as its resistance to halide corrosion, oxidation, and carburization, have led to the widespread use of alloy 6235 in chemical and petrochemical processing equipment, which are often exposed to highly damaging high-temperature conditions. ⑸ Nickel-chromium alloy 690 has the highest chromium content of all nickel alloys; it is suitable for manufacturing pressure equipment and possesses excellent resistance to oxidizing media. It can be effectively used in high-temperature concentrated mixtures of sulfuric acid, nitric acid, and hydrofluoric nitric acid, as well as in environments with oxidizing salts. The high chromium content also improves its resistance to sulfidation in high-temperature sulfidation environments. ⑹Nickel-chromium-iron alloy 825 is sometimes classified in the super austenitic stainless steel series as well, since this alloy contains about 30% iron. Like alloy 20, this alloy was developed primarily for various applications involving sulfur and phosphorus. Although alloy 825 has strong resistance to hydrochloric acid corrosion, it is susceptible to chloride pitting and crevice corrosion, especially in stagnant, airtight solutions. The high iron content in alloy 825 results in lower corrosion resistance to strong bases and halogens compared to alloys with higher nickel content. ⑺Nickel-molybdenum \"B\" alloy: Alloy B-2 exhibits excellent resistance to sulfuric acid, phosphoric acid, and hydrochloric acid under reducing conditions. It is particularly suitable for equipment used in processing hydrochloric acid of any concentration up to its boiling point temperature. Oxidizing compounds have an adverse effect on the corrosion resistance of this alloy; it is particularly noteworthy that strong oxidizers such as iron and copper salts can cause inclusions. The properties of the recently recommended alloys B-3 and B-4 are better than those of B-2, mainly because the undesirable microstructures are minimized. The nickel-chromium-iron-molybdenum \"G\" series alloy; alloy G-3 has corrosion resistance that exceeds that of alloys 400, 600, and 825 in many applications. This alloy is particularly resistant to corrosion by sulfuric acid and impure phosphoric acid, and can withstand erosion in both reducing and oxidizing environments. The newly developed alloy G-30 has better weldability and an overall improved corrosion resistance, especially in the heat-affected zone of welds. ⑼The nickel-chromium-molybdenum \"C\" alloy: In the chemical industry, where harsh corrosion conditions prevail, alloy C-276 is considered an excellent alloy due to its outstanding resistance to various acids, acid salts, and other corrosive substances encountered during chemical processing. Alloy C-276 is suitable for harsh environments such as those with moisture-containing chlorides and hypochlorites. Since alloy C-276 contains molybdenum, it is more resistant to pitting and crevice corrosion caused by chlorides. In the search for materials with better metallurgical properties and corrosion resistance than alloy C-276, several patented alloys were developed, such as C-22, 622, 59, 686, and C-2000. Among all alloys with roughly equal molybdenum content, the chromium content is **higher than that of alloy C-276. http://bbs.hcbbs.com/thread-118375-1-1.html

Hydrochloric acid, with the chemical formula HCl, is an aqueous solution of hydrogen chloride. Its appearance and properties are those of a colorless or slightly yellowish, volatile liquid with a pungent odor. Concentrated hydrochloric acid is highly volatile and corrosive; high concentrations can cause severe harm to the human body. It has a pungent odor and can react with many metals. It is one of the three strong acids; when combined with nitric acid in a 3:1 ratio, it forms aqua regia, which can dissolve gold. Hydrochloric acid can react with certain active metal powders to release hydrogen gas. It can produce highly toxic hydrogen cyanide gas when in contact with cyanides. It undergoes a neutralization reaction with alkalis, releasing a large amount of heat. It is highly corrosive. It is highly acidic; it reacts with bases to produce chlorides and water. It can react with most carbonates to yield carbon dioxide and water. It reacts with active metal elements to produce hydrogen gas. It also reacts with metal oxides to form salts and water. Hydrochloric acid is a strong acid that possesses all the characteristics of acids, such as the ability to neutralize bases to produce salts and water ； Can dissolve basic oxides ； It can dissolve carbonates and release carbon dioxide gas ； It can dissolve relatively reactive metals (such as zinc, magnesium, iron), producing hydrogen gas. Concentrated hydrochloric acid can dissolve the less reactive metal copper. Storage: Due to the high volatility of hydrochloric acid, the hydrogen chloride that evaporates from it combines with water vapor in the air to form small droplets of hydrochloric acid, which then disperse in the air. Therefore, hydrochloric acid must be stored in a sealed container; otherwise, over time its quality will gradually decline as will its concentration. Concentrated hydrochloric acid evaporates very easily in the air, and it is highly corrosive to skin and clothing. Therefore, special care must be taken when using it! Its corrosiveness stems from the oxidizing property of hydrogen ions, and the degree of oxidizing power is related to the concentration of hydrogen ions. Using the concept of limits, there is only one molecule of HCl in 1 liter of water; it’s possible that they won’t react with each other even after half a day. But if there is 1 mole of HCl, the reaction will occur easily. By diluting with water to reduce the concentration, the corrosivity is diminished. It cannot corrode pure copper; titanium and MONEL alloys can resist hydrochloric acid fairly well

Hydrochloric acid is a strongly reducing acid that is volatile. Hydrochloric acid-resistant precious metals and their alloys include tantalum, zirconium, platinum, gold, silver, etc. Alloys include zirconium alloys, Hastelloy, corrosion-resistant titanium alloys, and high-silicon ferrochrome containing molybdenum.

There are many types of corrosion, such as the corrosion of metals. It can be verified by putting livacity in hydrochloric acid to observe bubbling. Of course, there are other types of corrosion as well. For example, if a certain fruit is soaked in hydrochloric acid, the fruit gradually dissolves. Sometimes, when doing experiments, a little hydrochloric acid is accidentally spilled on the hands; if it isn’t treated promptly, it can cause itching, or in more severe cases, this demonstrates that hydrochloric acid is corrosive. As for the second question, be careful not to confuse it with corrosion caused by concentrated sulfuric acid. The reason wood turns black in concentrated sulfuric acid is that the organic compounds in the wood lose water and turn into carbon, which gives its surface a black color. Concentrated sulfuric acid has dehydrating properties, while neither dilute hydrochloric acid nor concentrated hydrochloric acid possesses such properties; therefore, hydrochloric acid cannot cause wood to turn black. I think it should be impossible for bubbles to form. Since the main component of wood is organic matter, it does not produce gas when reacting with hydrochloric acid. Inorganic salts in wood are also present in trace amounts, so no bubbles are formed. A low-alloy steel and its welded joints with excellent resistance to hydrochloric acid and sulfuric acid corrosion; the low-alloy steel contains, by mass percent, C: 0.001–0.2%, Si: 0.01–2.5%, Mn: 0.1–2%, Cu: 0.1–1%, Mo: 0.001–1%, Sb: 0.01–0.2%, P: 0.05% or less, S: 0.05% or less, with the remainder consisting of Fe and unavoidable impurities, and the acid corrosion resistance index AI of this steel is AI ≥ 0. Where AI, in mass%, is given by the following formula: AI/10000 = 0.0005 + 0.045×Sb% – C%×Mo%.

It is mainly acidic, as well as corrosive due to chloride ions. Metal used: Copper

The chloride ions produced can corrode austenitic stainless steel as well as carbon steel. Carbon steel equipment can be cleaned and descaled using hydrochloric acid. Hastelloy can withstand hydrochloric acid.