JP2880516B2 - Corrosion inhibitor composition and corrosion inhibition method - Google Patents

Description

The present invention relates to a corrosion inhibitor composition and a method for inhibiting corrosion.

The expression herein used during the "corrosion caused by chloride ions or the like" in, for example NaCl, CaCl _2, other corrosive deicers or produce similar corrosion or risk of some of the other resulting Means the corrosion caused by the product. The term also means that when dealing with corrosion control systems containing sodium fluorophosphate, such systems containing sodium fluorophosphate must not be used to control strongly acidic corrosion such as battery corrosion. This is because HF can be generated and HF is corrosive.

The corrosion control system is sodium fluorophosphate (also known as sodium monofluorophosphate, Na ₂ PO
₃ F), it contains at least a member selected from the group consisting of phosphonic acid derivatives of the following, preferred system in admixture with alone sodium fluoro phosphate or sodium silicate.

BACKGROUND OF THE INVENTION Sodium chloride is widely used as an anti-icing agent. Many means have been invented to solve the corrosion problem associated with its use. For example, corrosion of rebars in concrete has been reduced by pre-coating the rebar with epoxy or cathodic protection before adding the concrete.

The environment normally provided to strengthen the steel by the surrounding concrete is almost ideally suited to prevent corrosion of the steel. Properly placed, compacted and hardened high quality concrete gives the steel a highly alkaline, low permeability coating that protects against corrosion (passivation),
And minimize penetration of corrosion-inducing factors such as oxygen, water, and chloride. However, the inflation forces created by diffusion in concrete or through moisture, electrolytes and oxygen through hair cracks destroy the passive environment and establish an electrochemical corrosion cell, and ultimately by corroding the steel. Can destroy concrete. Chloride salts appear to be the ones that cause this type of erosion most severely. Thus,
Concrete structures exposed to harsh conditions, such as low quality concrete or poorly reinforced concrete coatings and bridge decks or marine environments exposed to deicing salt, are subject to particularly rapid degradation. Cheap. The importance of this problem and the economic impact of repairing and rebuilding highway structures has led to extensive research into the electrochemical behavior of steel in concrete and possible solutions over the past 15 years. Past and current research efforts have focused on the importance of factors such as coating depth, water / cement ratio, coated rebar, cement inhibitor mixtures, low permeability concrete, etc. in new structures and existing structures. Monitoring and remediation techniques, such as cathodic protection, membrane overlay
lay).

The low corrosion rate of steel in uncontaminated concrete is high at pH (12
1313) by forming a stable passivation layer of γ-Fe ₂ O ₃ on the steel surface in the presence of sufficient oxygen in the environment. There are two general mechanisms by which this passivation can be destroyed. (1) reduced alkalinity due to leaching of alkaline substances and / or partial reaction with CO ₂ , and (2) physical and electrochemical actions with chloride or other aggressive anions. Once the passivation of the steel is destroyed, the corrosion rate is dramatically increased by the formation of micro and macro corrosion cells. Oxidation of iron to ferric ions and formation of oxides occur at the anode (Equation 1), while reduction of oxygen occurs at the cathode (Equation 2).

^{(1) Fe → Fe 2+ +} 2e + O 2 → Fe 3 O 4 (2) 1/2 O 2 + H 2 O + 2e → 2OH - anode region and a cathode region corrodes steel may be widely separated. They depend on differences in chloride or other anions and oxygen concentrations and are affected by the pH near the steel-concrete interface.

Description of the Invention In general, the present invention relates to a novel corrosion inhibitor and a novel method of inhibiting corrosion.

In particular embodiments, Applicants have disclosed sodium fluorophosphate (a preferred member of Na ₂ PO ₃ F, also known as sodium monofluorophosphate), and the general formula R _n R ₁ N (CH ₂ PO ₃ H ₂ ) _{2 wherein} R _n and R ₁ are each independently selected from a member selected from the group consisting of alkyl, aminoalkyl and N-hydroxyalkyl, and n is an integer selected from 1 and 0 A corrosion inhibition system comprising at least one member selected from the group consisting of water-soluble salts of phosphonic acid derivatives and containing at least one member that inhibits corrosion of reinforcing bars in contact with water,
Invented is a method for suppressing corrosion caused or caused by chloride ions or the like, which method is characterized by being placed on the surface of reinforced cement containing reinforcing steel. Water allows for the replacement of corrosion control systems such as sodium fluorophosphate on rebar.

The present specification also discloses an anti-icing agent comprising a system having at least one member selected from the group consisting of sodium fluorophosphate and the above phosphonic acid derivatives.

Anti-icing agents are known, and anti-icing agents are generally capable of lowering the freezing point of water and have other suitable properties that need not have a substantial adverse effect on the environment or its intended use. Means (For example, if the intended use is for roads, the deicing agent must not be slippery.) This may be glycol (eg, ethylene glycol), calcium magnesium acetate, methanol, calcium chloride, magnesium chloride,
Includes urea, sodium formate and other commonly available anti-icing agents. The deicing agents also include corrosive deicing agents, and Applicants' corrosion inhibitors are particularly beneficial for such corrosive deicing agents.

Generally, at least 50 deicers, including corrosion control systems
Contains, by weight, preferably at least 70% by weight of an anti-icing agent.

Also disclosed herein is an anti-icing agent comprising a system containing at least 85% by weight of an anti-icing agent and at least 0.25% by weight of sodium fluorophosphate.

The present specification also discloses a method for preventing freezing on an outdoor surface, which comprises placing one of the above-mentioned antifreezing agents on the outdoor surface.

The present invention also relates to a method for preventing freezing on an outdoor surface, which comprises placing one of the above-mentioned antifreezing agents on the outdoor surface.

The present invention is also directed to a number of suitable carrier corrosion inhibitor systems. For example, the carrier may be in a suitable vapor, liquid or solid phase, the carrier may be a deicing agent,
Includes paints, coatings, diluents, emulsions, suspensions, solvents and air spray sprays, but are by way of illustration and not limitation.

Some preferred embodiments include sodium fluorophosphates, especially aqueous solutions of sodium fluorophosphate and sodium silicate, more preferably those aqueous solutions that are substantially near saturation, ie, as saturated as possible to be diluted upon use. Containing an aqueous solution close to Other preferred embodiments include coatings and paints comprising sodium fluorophosphate.

The invention is particularly applicable to reinforced concrete surfaces, surfaces such as iron-containing concrete, surfaces exposed to air, chloride ions, etc. and metal car structures, bridge structures, culvers, and pipes for electricity, gas, water and sewage. And especially for outdoor metals such as outdoor surfaces. The invention is also very useful for galvanized steel and to a lesser extent other metals and metal-containing surfaces. Such exposed surfaces may be sprayed, coated, painted or immersed in a container containing a corrosion inhibitor system, either dry or wet.

In contrast to anti-icing agents, corrosive anti-icing agents are used for sodium chloride, calcium chloride, magnesium chloride, potassium chloride, sodium formate, other corrosive anti-icing agents and other products with ions that act as chloride ions. Anti-icing agents which are susceptible to corrosion and contain such salts.

Corrosion inhibiting systems containing fluorophosphates or systems containing fluorophosphates can be used alone or with other additives, if desired, with or without other additives, such as sodium silicate. A fluorophosphate in combination with a component is meant. For example, soil conditioners such as CaSO ₄ , urea, other mineral-containing substances, nitrogen substances, etc. may be used as additives in amounts that do not substantially affect the anti-icing properties of the anti-icing agents described below.

Further, the invention features placing the system containing sodium fluorophosphate on a metal surface exposed to air.
The present invention relates to a method for suppressing corrosion on a metal surface exposed to air, chloride ions, and the like, which cause corrosion as caused by chloride ions.

The present specification also discloses products containing at least residual amounts of the corrosion control system, which may be in the form of a corrosion control system or the action of the corrosion control system on the product or a component of the product, or aging, cleaning, rain, etc. Means a product that is included as a residual amount derived from These products generally have outdoor surfaces exposed to air, chloride ions, and the like. For example, concrete, rebar, metal surfaces, generally bridge structures, metal vehicle structures and others described in the specification.

Preferred method of practicing the present invention Preferably, the present invention comprises a system comprising sodium fluorophosphate with or without sodium silicate comprising at least 0.25% by weight, preferably 2-5% by weight.
An anti-icing agent having reduced corrosive properties, characterized in that it contains salt (NaCl) along with% by weight. The weight ratio of sodium fluorophosphate to sodium silicate may be, for example, from 1 to 10: 1 to 2.5, preferably about 1: 1. These anti-icing agents are most preferred because the anti-icing properties of the salt are substantially maintained and their corrosive properties are suppressed against rebar, especially when used with reinforced concrete.

There are a number of methods that can be used to apply the deicing agent. For example, anti-icing agents may be used with sand. Anti-icing agents having reduced corrosion properties may be dry-mixed or wet-mixed, solid-mixed, or mixed in-place where needed. For example, an anti-icing agent may be made by dry mixing sodium chloride with a fluorophosphate containing system. The system containing the fluorophosphate may also be diluted to a minimum with a solvent or diluent suitable for the particular end use, such as water, glycol, sand, preferably with sufficient water to achieve the desired viscosity. May be dissolved, suspended or emulsified, whereby the system containing sodium fluorophosphate can be soaked in that it hits sodium chloride and / or sand, for example, before the system is placed on a surface such as a concrete surface. , Can be easily sprayed on sodium chloride, or sprayed against sodium chloride in a plant or in a salt and / or sand dispersion vehicle. Also, the system may be sprayed with sodium chloride or otherwise distributed in sodium chloride. The sodium chloride may be carried by an endless conveyor such as a belt conveyor or other means. The spray of the system can be applied to a desired amount of a system containing sodium fluorophosphate in a novel deicing agent having reduced corrosion properties, for example 0.25 to 10% by weight, or more if desired, preferably 2 to 10% by weight. It is carried out to obtain 5% by weight.

This deicing agent, such as a salt and corrosion inhibitor system, having reduced corrosion properties, nevertheless has good icing which is substantially unchanged, such as friction, freezing point, ice penetration rate, and ice melting rate Has the properties required for inhibitors.

Other methods of practicing the invention Anti-icing agents having corrosive properties may include other anti-icing agents as described above in place of sodium chloride, and what has been described for sodium chloride is generally that of these other corrosive agents. Applies to anti-icing agents.

Corrosive deicing agents include not only fluorophosphates with or without sodium silicate, but also less preferred fatty acids such as those having 8 to 24 carbon atoms. It may be used with or without an amide (eg, an acceptable toxic amount of cocoamide). Also, although less preferred, salts of the above phosphonic acid derivatives may be used. Typical examples of these phosphonic acid derivatives include the sodium salt of triethylenetetramine hexakis (methylene phosphonic acid) or other compatible soluble salts and the sodium salt of ethylhexylimino bis (methylene phosphonic acid) or combinations thereof.

The process for preparing these phosphonic acid derivatives comprises reacting an amine with formaldehyde and phosphonic acid. The deicing agent may be pelletized if desired.

The corrosion inhibitor system described above can be used with or without anti-icing agents to inhibit corrosion. Also, the corrosion inhibitor system may be an aqueous medium or a solution that forms an emulsion, suspension or paint for some applications as a solution, such as a saturated aqueous solution or coating, with or without an anti-icing agent. It can also be in a suitable carrier, either gas, liquid or solid, such as another medium. The paints, emulsions, suspensions or coatings may be used to coat metals such as rebars, car structures, bridge structures, plumbing for electricity, gas, water and sewage, culvers or other outdoor metal surfaces, as desired. obtain. Air, as well as other suitable gases, may be used to disperse the corrosion control system.

EXAMPLES The following examples serve to illustrate particular aspects of the present invention and illustrate some of the new anti-icing agents, new corrosion inhibitors systems, new methods and new applications compared to the prior art. Demonstrate.

Examples 1-4 The test used was ASTM-G-31-72, revised in 1985 for corrosive deicing agents using the system described in Table 1. The corrosion rate that causes weight loss is μm / year (mil /
Year (referred to as mpy)). As can be readily seen, systems containing fluorophosphates and silicates have a significant pronounced effect on reduced corrosion as seen in the examples.

Example 5 The following data shows the effect of pH on the rate of corrosion by sodium chloride alone or in combination with the following using the methods described in Examples 1-4.

A is Na ₂ PO ₃ F and B is a 1: 1: 1 mixture of Na ₂ PO ₃ F: Na ₂ SiO ₃ : sodium lignosulfonate.

Examples 6-7 The data below also demonstrate the reduced corrosion properties of systems containing sodium chloride using the following procedure.

Rebar / concrete specimens lever stock about 1.3 cm _^(1/2 inches) (rebar stock) and 1: 1: 5 was processed from the concrete mixing setting ratio (Portland cement: water sand). Sodium chloride is Cl approximately 12 kg / m ³ to the mixing water (20 Bond / cubic yards) ^- was added in to produce a concrete chloride amount. The concrete cover was 5 mm and the exposed rebar area was 14 cm ² . The corrosion rate was measured using the AC impedance measurement method. In continuous AC impedance measurements, a sine wave of fixed amplitude, typically on the order of 10 mV, is applied to embedded steel at decreasing frequencies, and both the phase shift and modulus of the impedance of the steel are monitored as a function of frequency. This teaching is based on F. Mansfed.
ld) “Recording and Analysis of AC Impedance Dat
a for Corrosion Studies-I "(Nace 36 5 No. 301-307
May 1981 and 38:11, 570-580, November 1982) and K. Hlad ky, L. Callow,
"Corrosion Rates from Imped" by J. Dawson
ance Measurements: An Introduction "(Br. Corro J., 15
Vol. 1, pages 20-25, 1980).

Examples 8-19 In the following examples, the corrosion current during the macrocell corrosion test was monitored using a reinforced cement slab as follows.

Two mats of rebar were cast in concrete using AE concrete of average quality. Various amounts of sodium chloride were mixed into some of the top mat layers to promote corrosion and simulate the environment present in the old bridge deck. A weir was placed on top of each slab and a 6% solution of the deicing product was pooled to a depth of about 1.7 cm (2/3 inch). The solution was replenished every two weeks.

An instantaneous off / on switch with a top and bottom set of rebars electrically connected and a 1.0 ohm resistor in series was placed between the two mats.

Corrosion current flowing between the top and bottom mats,
It was measured as the voltage drop across the resistor when the switch was on (normal position). The driving force (potential difference) between the top and bottom mats was measured as the "immediate off" potential between the two mats (the switch was depressed instantaneously (off) and the voltage was read within 2 seconds. T). The corrosion potential of the top mat was measured against a saturated calomel electrode with the switch in the normal "on" position.

In Table 3 [Cl ^-] means kilograms of chloride per cubic meter (lb of chloride per cubic yards), the same batch as used for the sample W and the like used for Examples 8, 12 and 16 .

Analysis Sample C and the reinforcing steel of Example 8 were analyzed for corrosion products.

The corrosion product layer of Sample C consists mainly of iron oxides / hydroxides with small amounts of sodium and chlorine (from solution) and silicon (silica from the aggregate mixture) present,
The concrete side of the interface indicates that calcium is present as both oxides / hydroxides and carbonates.

The corrosion product layer of Example 8 is more complex. This layer is quite thick and has a higher calcium content than the unrestrained surface. Calcium exists as an oxide / hydroxide of calcium without showing any carbonate species present. Also shown are the amounts of chromium, nitrogen and aluminum present in the film. Trace amounts of phosphorus were also detected.

As a tentative explanation, the effect of the inhibitor appears to be a local environmental change due to the prevention of a reaction or reaction with concrete components. The main difference between inhibited (Example 8) and uninhibited (Sample C) is the amount and nature of calcium present in the corrosion product film. Carbonation of the concrete layer, together with the presence of chloride, is an essential precursor to the corrosion of steel bars. The inhibitors of the present invention affect this carbonation reaction, and thus the mechanism of corrosion inhibition allows the maintenance of a stable passive film rather than the incorporation of inhibitor compounds into the film, forming a more protective layer on the surface. It was found that this was equivalent to changing the local environment.

Example 20 The following data serves to illustrate the reduced corrosion of a 4% corrosive deicing solution. Inhibition rate (%) is Na ₂ PO ₃
It is calculated as the percentage reduction in corrosion rate relative to the corrosion rate of a similar deicing solution without the F system.

Example 21 The following data serves to illustrate the effect of the concentration of the Na ₂ PO ₃ F system over time using the following 4% sodium chloride deicing solution.

Example 22 The following data serves to illustrate the reduced corrosion properties of the preferred corrosive deicing agents for various metals.

Examples 23-24 The following examples combined with Na ₂ PO ₃ F, and Na ₂ SiO ₃ and / or reduced corrosion characteristics of deicer having lignosulfonates Na ₂ PO ₃ F alone or Na ₂ SiO ₃ This is due to Na ₂ PO ₃ F and not to lignosulfonate.

Na ₂ PO ₃ F, and Na ₂ SiO ₃ seawater solution the inhibitor mixture - with respect to mild steel probe (aqueous treatment Example 23) in, and small rebar - its effect on the corrosion of reinforcing bars in the concrete in the probe (Example 24) Was tested.

23-Water-based treatment 0.9 c diameter immersed in 3% w / w NaCl + inhibitor below
Polarization resistance of a 1018 carbon steel cylindrical electrode, m, 1.2 cm high.

24 Concrete Probe about 1.3 cm _^(1/2) lever stock and mixing set ratio inches) 1: 1: 5 (Portland cement: water: rebar / concrete specimens of concrete sand) Example 6 and 7
Processed as follows. The concrete cover is 5mm,
The exposed rebar area was about 35 cm ² . Probes were exposed to a solution of 3% NaCCl + inhibitor (at the indicated concentration) for the following days and subsequently analyzed (per corrosion rate) using the AC impedance technique.

Example 25 This example illustrates the corrosion inhibiting properties of a coating, such as a paint having a sodium fluorophosphate system.

For the purpose of this experiment, 2% (w / w on paint) Na ₂
Add any amount of PO ₃ F to a commercially available paint, ie, an oil based semi-gloss paint, for about 2.5 cm × about 5 cm (1 inch × 2 inch) and about 5 cm × about 10 cm (2 inch × 4 inch) Of mild steel C1010 coupons were exposed to a cyclic immersion, a humidity test operation according to ASTM standard D1654. For comparative purposes, Samples A and B were treated with a "Rustclad" corrosion control paint and a "Krylon" corrosion control paint, respectively.

The results showed that the Na ₂ PO ₃ F blend paint performed better than “Last Clad” and outperformed “Crylon” treated specimens. From the foregoing, it is readily conjectured that other suitable emulsions and suspensions may also be used. In all cases, the corrosive effect was lower than when the immersion was performed in a salt + Na ₂ PO ₃ F solution.

Experiment Cold rolled C10 of about 2.5 cm x about 5 cm (1 inch x 2 inches) and about 5 cm x about 10 cm (2 inches x 4 inches)
Ten mild steel coupons were prepared by applying the specimen twice with the "last clad" metal primer followed by two coats with the following paints.

Example 25: Commercial paint mixed with 2% (w / w based on paint) Na ₂ PO ₃ F, ie oil-based semi-gloss (white) paint for internal use.

Sample A: Last clad (white gloss) Sample B: Crillon (silver) “X” was scribed on one surface of each coupon with a sharp knife. 3% deicing solution (NaCl or NaCl + Na ₂ PO ₃ F (9
7.6: 2.4)) plan to immerse at 55 ° C for 16 hours and then suspend in a 55 ° C water bath for 8 hours on a solution in a humid atmosphere
The coupon was cycled according to TM Standard D1654). Relative corrosivity was determined by visual ranking of rust contamination according to the guidance provided by the ASTM procedure.

Results The assessment of corrosion damage in both scribed and non-scribed areas using the criteria established in ASTM D1654 is shown under the scribed and non-scribed area items. FIG. 1 shows about 5 cm × after exposure to a salt solution and a salt + Na ₂ PO ₃ F solution, respectively.
Figure 4 represents the results obtained for a coupon of approximately 10 cm (2 inches x 4 inches).

The results show that Na ₂ PO ₃ F has good corrosion inhibition properties with respect to the paint. Na ₂ PO ₃ F is relatively non-toxic,
On the other hand, most corrosion inhibitors added to commercial paints are chromium-based, which is thought to be not only toxic but also environmentally damaging.

Having described the invention, many modifications will be apparent to those skilled in the art without departing from the spirit of the invention, which is set forth in the following claims.

[Brief description of the drawings]

In the drawings which show a special embodiment of the invention, FIG. 1 shows a salt solution and salt + Na according to Example 25 compared to the prior art.
It represents the results obtained for coupons ₂ PO ₃ F about 5 cm × about 10cm after exposure to each of the solution of (2 inches × 4 inches).

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Darren F. Laureth Canada H1M 2 El 7 Quebec Montreal Cadillac Street 5732 (72) Inventor Terrance E-Peel Canada J0P1J0 Quebec Hudson Heights Pio Box 529 (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 41/67, 41/62

Claims (6)

(57) [Claims] (1) sodium monofluorophosphate and a compound represented by the general formula (R ₂ ) _n R ₁ N (CH ₂ PO ₃ H ₂ ) _2-n (wherein R ₁ and R ₂ are each independently an alkyl, amino A group selected from the group consisting of alkyl and N-hydroxyalkyl, and n is an integer selected from 1 and 0) at least one selected from the group consisting of water-soluble salts of phosphonic acid derivatives represented by A corrosion inhibitor composition comprising a compound. 2. The corrosion inhibitor composition according to claim 1, wherein said compound is sodium monofluorophosphate. 3. The compound represented by the general formula (R ₂ ) _n R ₁ N (CH ₂ PO ₃ H ₂ ) _2-n (wherein R ₁ and R ₂ are each independently alkyl, aminoalkyl and N A hydroxyl group selected from the group consisting of -hydroxyalkyl, and n is an integer selected from 1 and 0). Composition. 4. The method according to claim 1, further comprising a carrier.
The corrosion inhibitor composition according to any one of (3). 5. A method for suppressing corrosion caused or caused by chloride ions or the like in reinforced concrete containing a reinforcing bar, the method comprising the steps of:
The method of any one of the preceding claims, comprising placing the corrosion inhibitor composition of paragraph (1) on the surface of the reinforced concrete. 6. A method for inhibiting corrosion on metal surfaces exposed to air and chloride ions, comprising the steps of:
(4) The method according to any one of (4), further comprising placing the corrosion inhibitor composition according to any one of (4) on the metal surface.