What Are the Commonly Used Rust & Corrosion Inhibitors? How Are They Applied to the Metal Processing Fluids?
The introduction of the advantages and disadvantages of the common used rust and corrosion inhibitors, and the analyzation of their application techniques in the metal processing fluids.
Borate/Boric Acid Ester
Borate/Boric Acid Ester is a widely used water-soluble anti-rust agent at present, which is especially effective for the rust prevention of cast iron, and can be used in synthetic cutting fluid, semi-synthetic cutting fluid and water-based grinding fluid.
01 Borate
Good rust prevention and low cost. In the solution, it is easy to take the hydrolysis reversible reaction, and with the consumption of alkali, the boric acid will precipitate and corrode the metal.
02 Boric Acid Ester
High alkali reserve, and stable pH value of the system. It has the good anti-friction and anti-wear performance. And it has certain bacteriostatic and bactericidal functions.
If the borate/boric acid ester is used alone, the effect is not ideal, so it needs to be combined with other rust prevention agents. Boric acid ester combined with the different carboxylate salts has the good anti-rust properties for the ferrous metals.
Disadvantages: for the long-term use, it is easy to sticky, affecting the cleaning.
Molybdate
Molybdate: nitrite = 2:3, the total concentration of 5mg/L, has a good corrosion inhibition on the carbon steel.
Sodium molybdate: MEA (monoethanolamine) = 1:5, has a good corrosion inhibition effect on the steel
Molybdate +BTA+ sodium benzoate + amine has a good anti-corrosion effect on the steel and the cast iron.
Molybdate is a low toxicity and no pollution corrosion inhibitor. As a corrosion inhibitor, the advantages are as follows:
① The corrosion inhibition effect is good, and the combination with other corrosion inhibitors can prevent the spot corrosion.
② It has the good corrosion inhibition effect on the carbon steel, the copper, the brass and the aluminum and other common metal materials
③ Low toxicity
④ It is widely used and effective in both soft and hard water
Disadvantages: the dosage is relatively large, and the cost is relatively high.
Sulfonates and Other Oil-Based Rust Inhibitors
01 Petroleum Barium SulfonateT701
Solids: 50%, liquids: 50%. The solid T701 has the good oil solubility after heating, and has the good anti-rust properties for the black and non-ferrous metals. It is used for anti-rust oil, oil-based products, emulsified oil and micro-emulsified oil.
02 Sodium Sulfonate T702
Petroleum sodium sulfonate: has the strong hydrophilicity, corrosion inhibition on metals, good rust resistance and emulsification properties, used in oil-based products, emulsified oil and micro-emulsified oil.
Synthetic sodium sulfonate: prepared by the heavy alkyl benzene sulfonation, neutralization, decolorization. With the HLB value of about 12 and the strong hydrophilic, corrosion inhibition on the metals, it is a good anti-rust agent and emulsifier. The hydrophilicity is obviously stronger than sodium petroleum sulfonate, the color is lighter, the emulsification range is wide, and the deployment is convenient, so it is an ideal additive for the preparation of micro-emulsified oil.
03 Zinc Naphthenate T704
Good oil solubility, and good rust resistance to the steel, the copper and the aluminum. Poor rust resistance to the cast iron if used alone. It needs to be combined with T701 to achieve the good results. It is suitable for the oil-based products, the emulsified oil and the micro-emulsified oil. (Dosage: 3-10%)
04 Barium Dinonylnaphthalene Sulfonate T705
It has the excellent anti-rust properties for all kinds of metals, good oil solubility stability, good lubrication and anti-wear properties, and good stability in wet conditions. Used as an anti-rust additive in various petroleum and synthetic lubricants and greases. Used as an anti-rust agent in petroleum ether cleaning agent and water displacement anti-rust liquid.
05 BENZOTRIAZOLE T706
The product is a white to light yellow acicular crystal, slightly soluble in water, and soluble in organic solvent such as alcohol, benzene, toluene, chloroform, dimethyl acylamide, etc., prepared from o-phenylene diamine and sodium nitrite. It provides the lubricant with good antirust to copper and copper alloys; preferable antirust effect on silver and silver alloy; and possesses favorable corrosion inhibition performance.It is used primarily in antirust oil and grease. It also serves as gas phase corrosion inhibitor for copper and copper alloy; silver and silver alloy circulation water treatment agent, etc.
06 Metal Passivator KHC3039
It is currently an ash-free liquid metal passivator, antioxidant and anti-wear additive, widely used in various automotive and industrial lubricating oils and metal working fluids. It can provide excellent copper corrosion inhibition and anti-oxygen and anti-wear properties.Used for various automotive and industrial lubricating oils, greases and metal working fluids.An ash-free liquid metal deactivation additive.It can be directly added to the customer's product formula. Compatibility should be tested before adding. The recommended dosage is 0.1%- 0.5%.
07 Water Soluble Copper Corrosion Inhibitor KHC3042
It is a methyl benzotriazole derivative, soluble in water and ethylene glycol system, used as a metal deactivated agent. It can replace solid Benzotriazole and solid methyl benzotriazole, effectively protect yellow metal and prevent cobalt spillover. Its combination with the conventional carboxylate rust inhibitor can provide corrosion protection for a variety of metals.All water based systems with PH>7: antifreeze (engine coolant), high water based hydraulic fluid (HFC), water/glycol hydraulic fluid (HFC), metal working fluid (emulsion and synthetic fluid), etc.The recommended dosage is 0.1%-0.5%.
Use with nitrite is not recommended because it may form nitrite amine.It is recommended to use carboxylate rust inhibitors together, which can have a synergistic effect.
Fatty Acid Salts, Fatty Acid Esters/Amides
(1) Fatty acid salts: oleic acid / alkamine salt, tall oil/ alkamine salt, C21 carbon dibasic acid/ alkamine salt, dimeric acid/ alkamine salt, etc.
(2) Fatty acid esters: Dehydrated sorbitan monooleate (Span-80), etc.
(3) Alkylamide: alkolamide, castor oil maleamide, nitrogen containing heterocyclic boramide, tall oil amide, etc.
Advantages: with the emulsification, the cleaning, the lubrication and the rust prevention functions all together. In the system with high oil content, the rust prevention is good, but in the low oil content system, the rust prevention is normal.
Disadvantages: large foam, and easy to corrupt.
Caprylic Acid, Neocapric Acid / Isononaic Acid
Caprylic acid, neocapric acid / isononaic acid is mainly used in the synthetic cutting fluid, especially in the total synthetic system containing polyether. In the alkaline system it can couple polyether, improve the solubility of polyether in the alkaline system, and assist the lubrication of polyether. Itself has a certain anti-rust performance, and can improve the film formation of other anti-rust agents on the metal surface. It can also be used as a balancing agent in micro emulsification and emulsification systems to adjust the balance of the system.
Disadvantages: it is relatively smellier, and the rust prevention is normal if used alone.
Diacid
01 Sebacic acid
It is generally prepared by separating castor oil after heat saponification and hot cracking. Castor oil is one of the most deeply processed vegetable oils in the world, and sebacic acid is its important downstream product, which is widely used as an anti-rust agent for water-based products.
Advantages: As a water-based rust inhibitor, its hard water resistance is good, and the foam is relatively small.
Disadvantages: the rust resistance is normal, and the price has soared repeatedly in recent years, and the cost performance has become lower and lower.
02 Undecane / Dodecane Dibasic Acid
The long chain dibasic acid does not exist in the nature, but it can be combined with long chain dibasic acid by the chemical method. However, the chemical production of long chain dibasic acid has shortcomings such as the technology and equipment requirements, and the high energy consumption, etc. At present, the production of long chain dibasic acid is gradually adopted by the microbial fermentation.
Advantages: As a water-based rust prevention agent, it has the good rust prevention.
Disadvantages: Poor resistance to the hard water, the large bubbles, easy corruption. In recent years, the price has soared again and again, the cost performance has become lower and lower.