US3079220A

US3079220A - Inhibiting corrosion with chromiumquaternary ammonium salt compositions

Info

Publication number: US3079220A
Application number: US839077A
Authority: US
Inventors: David B Boies; Crowther Joan; Walter J Ryzner
Original assignee: Nalco Chemical Co
Current assignee: ChampionX LLC
Priority date: 1959-09-10
Filing date: 1959-09-10
Publication date: 1963-02-26
Anticipated expiration: 1980-02-26

Description

iteta This invention relates to a new method for inhibiting corrosion in industrial process Water systems. More specifically, it relates to non-corrosive aqueous liquids which contain minor amounts of corrosion inhibiting chemicals.

In under Water systems in which water moves through such units as condensers, engine jackets, cooling towers and the like, corrosion is frequently quite severe due to the fact that water is concentrated several times during the course of the various processes. Such systems which are for the most part, recirculating types, contain equipment which uses as its structural material such metals as iron and steel, brass, copper, admiralty metal as well as minor amounts of zinc and other non-ferrous metals.

One of the best inhibitors for rendering such systems non-corrosive are the well known alkali metal chromates. While chromates are economical and give good results, in many cases it has frequently been the experience of the art that pitting and tuberculation of the.various surfaces occurs when chromates are used alone. The problem of pitting and tuberculation which sometimes occurs with chromate inhibitors may be mitigated using chromates in conjunction with phosphates. Although such combinations of inhibitors have proven to be of value in protecting industrial process water systems, they are not entirely satisfactory from all standpoints.

Many attempts have been made to develop new inhibitors for aqueous systems of the type described above, with much effort being directed towards discovering an organic inhibitor of the so-called film forming type. Materials such as amine compounds, quaternary ammonium salts, and certain carboxylic acids which are known to be efiective inhibitors for many types of systems have failed to protect industrial process water systems at low economical dosages.

It would be a valuable contribution to the art if an inhibitor containing an organic film forming component could be devised for industrial process systems which would be effective at low economical dosages and would be successful in preventing tuberculation and pitting of metals in contact with such systems.

It has been discovered that extremely'valuable corrosion protection to metals in contact with industrial process waters may be afforded by treating such systems with a combination treatment which comprises a water soluble hexavalent chromium compound in conjunction with a specific type of water dispersible quaternary ammonium salt. In a preferred embodiment, the water soluble hexavalent chromium compounds and the water dispersible quaternary ammonium salts are advantageously combined with minor amounts of certain compounds capable of producing in aqueous solution a heavy metal cation such as zinc, cobalt, nickel, mercury and trivalent chromium cations.

The various compositions described above as the inhibitors of the invention are preferably used at certain I amazze Patented Feb. 26, l2$63 dosage levels in the Water to provide optimum results. In the case of the hexavalent chromium compounds, the dosage is maintained at between 10 and 200 parts per million (expressed as CrO Preferably the dosage is maintained between 15 and 50 parts per million. The quaternary ammonium salt is maintained in the Water at a dosage level ranging at generally between 0.5 to 10 parts per million and preferably between 2 and 6 parts per million. In the case of the heavy metal compounds, the dosage is maintained at between 0.25 and 10 parts per million with the preferred range being at 2 to 6 parts per million. These latter dosages are expressed in terms of the metal rather than the total compound with which it is associated.

In order to achieve optimum results, it is beneficial that the pH of the water be maintained within certain specific ranges. As a general rule, these ranges may vary between 5.5 and 8.5, although the best results are achieved when the pH is kept within the ranges of 6.5 to 7.5.

The hexavalent compounds of chromium are most suitably chosen from the alkali metal chromates and dichromates such as sodium dichromate dihydrate, sodium chromate (anhydrous), sodium chromate tetrahydrate, sodium chromate hexahydrate, sodium chromate decahydrate, potassium dichromate, potassium chromate, and the like.

The quaternary ammonium salts used in the practice of the invention may be selected from a large group of known and commercially available materials. It is essential to the practice of the invention that the particular quaternary ammonium salt must contain at least 8 carbon atoms and preferably at least one acyclic organicradical of at least 12 carbon atoms in chain length. The higher acyclic organic radical may contain as many as 22 carbon atoms. Preferably the higher acyclic organic radical should be from 16 to 18 carbon atoms in chain length. A preferred group of quaternary ammonium salts are the quaternary ammonium chlorides having the following general structural formulae:

where R is a higher aliphatic group of from 16-18 carbon atoms in chain length, e.g., hexadecyl, heptadecenyl, octadecyl, and octadecenyl, and R R and R are lower aliphatic carbon groups of from 1-6 carbon atoms in chain length, e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, and hexyl. Another useful group of quaternary ammonium salts are the higher aliphatic substituted imidazolinium salts.

For purposes of illustrating several quaternary ammonium salts of the type which may be used in the practice of the invention, Table I is presented. Also included in this table are certain amines which are considered inoperative.

TABLE I Quaternary Ammonium Salts A. lmidazolinium salts:

(l) Z-methyl-l-(Z hydroxy ethyl) 1 benzyl imidazolinium chloride (2) 2-coco-l-(2-hydroxyethyl) -1-benzyl imidazolinium chloride (3) 2-coco-l-(hydroxyethyD-l (4 chlorobutyl imidazolinium chloride 3 l (4) 2-coco-1-(2-hydroxyethyl)- 1 octadecenyl imidazolinium chloride (5) 2-tall oil fatty-1-(2-hydroxyethyl)-l-benzyl imidazolinium chloride 1 (6) 2-tall oil fatty-I-(Z-hydroxyethyl)-1-(4-chlorobutyl) imidazolinium chloride 1 (7 2-heptadeccnyl-1- (Z-hydroxyethyl) -1- l-chlorobutyl) irnidazolinum chloride (8) Z-heptadecenyl-1-(2-hydroxyethyD-l-benzyl imidazolinium chloride (9) Z-heptadecyl-l-(hydroxyethyD-l .octadecyl imid azolinium ethyl sulfate i B. Aliphatic quaternariesi (10) Dodecyl trimethyl ammonium chloride: (ll) Hexadecyl trimethyl ammonium chloride (12.) Octadecyl trimethyl ammonium chloride (.13) Coco trimethylammonium chloride 14) Soyatrimethyl ammonium chloride (15) Tallow trimethyl ammonium chloride l6) Dicoco dimethylammonium chloride 17.) Cocoamine Rx 15 moles EtO quaternized with methy h o e (18) Octadecyl amine Rx 2 moles EtQ quaternized withmethyl chloride (19;),Oetadecenyl amine R2; 2 moles EtQ quaternized withmethyl-chloride (19A,) D v r s atsd. l l d m y o nium chloride C. Amines;

(-20) Soyaamine- (:21 Hydrogenated tallowamine (2 ,Coco amine 1), Miscellaneous quaternary ammonium compounds:

' (23) Lauryl isoquinolini-um bromide. (24) Cetyl isoquinolinium bromide (25)" Lauryliisoqinolinium chloride (26 Alkyl (C H to C t-I dimethyl3,4,-dichlorobenzyl ammonium chloride and alkenyl- (C to C- )-'.dimethyl ethyl; ammonium bromides injtbe ratio 5:1 (27) OctadecenyI-Q'dimethyl benzylammonium chloride (28) l dodecyl-izrbenzyl pyridinium bromide (29*). l-methyl-Lethyl piperidinium bromide (30:) Hexadecyl pyridinium bromide. (31) N.-soya-N'ethyl morpholinium ethosulfate [From the above table it will be seen that the quaternary ammonium salt may have a wide variety of substituents just so long as theycontain a higher alkphatic group of the type previously specified. Other useful imidazolinium salts which meet the specifications set forth herein are disclosed in Rydell, US. 2,733,325. The preferred quarternary ammoniumsaltshave only one higher saturated or unsaturated aliphatic group 'of at least 12 carbon atoms since they are most readily dispersible in the aque O'us systems in which they are employed. The higher aliphatic radicals may be mixed, as, for. example, those radicals derived from vegetable oils and animal fats. The expression dispersible when referring to thequa ternary ammonium salts is meant to refer to thosematerials that are either water soluble or thosethat may be colloidally dispersed in aqueous. systems at use concentrations.

' The heavy metal cations are derived from their water soluble salts or bases. Examples of typical compounds that fall within this category are the following: zinc sulfate, cobaltous'chloride, nickel iodide, mercuric acetate, chromic chloride, zinc chloride, cobaltous sulfate, and mercurous chloride.

When making concentrated solutions for the purpose of feeding, itis frequently desirable to use the acidic salts of the heavy'metal materials such as, for instance, zinc sulfate and also to use an acid or an acidic material Essentially free from rosin acidcornponents.

such as sodium hydrogen sulfate or sulfamic acid whereby the pH of the resulting concentrated solution is adjusted between 3.5 and 5.

In using the inhibitors described above, it is helpful if the hexavalent chromium compounds and the heavy metal ionizable compound is combined into one formulation. The quaternary ammonium salt is used as a separate entity, since experience has shown that combining all the ingredients into a unitary product causes a reaction to occur between the chromate and the quaternary ammonium salt, which reaction forms an insoluble material. When fed separately to industrial process water systems at the dosages previously specified, no such insoluble reaction products are formed. Typical products The polyphos-phate in Formula A is. added for the purpose of stabilizing the calcium carbonate which may be present in the water. If calcium carbonate does. not present a problem in the water to be treated, the polyphosphateis omitted. However, since this. process does not adversely affect the usefulness of the treatments, it is desirable to use it in most cases. The phosphate may be used in dosages of .5 to 2 parts per million, although dosages as high as l to 9 par-ts per million may also be used, butgenerally the dosage need never-exceed l part per million. It should be noted that at these dosage levels the" phosphate neither adds-nor detracts from the inhibiting properties of the compositions described abo-ve.

EVALUATION OF THE INVENTION T he. test methods used to determine the efiicacy of the inventionwhen used to inhibit the corrosion of industrial process waters are of three. types. These test methods are .describedbelow in detail under the headings of test methods A, B, and C.

Test method A.The specimensused are weighed, sandblasted mild steel coupons (SAE 1010) 1 inch wide by 2 inches long by 20 gauge. 500 ml. of the test water was used. The treatment was added (generally from astock solution) and the pH adjusted to 6.5 with sulfuric acid or sodium hydroxide. The test water was prepared to simulate a typical cooling water. This synthetic water had the following composition:

-P-m- Total hardness (as CaC O 400 Calcium hardness (as CaCO 250 Magnesium' hardness (as CaCO 150 Total alkalinity (as CaCO 5 Sulfate (as Na SOQ 1400 Chloride (as NaCl)' SOQ The test coupon was immersed and the solution stirred at 1750 rpm. with a bell shaped stirrer for 24 hours. At the end of this time the coupon was removed from the water and air dried. The coupon was then examined and scored according to the weight loss of the coupon and visual evaluation of factors such as pitting and deposit. The test was run at F.

Test method B.Thesecond laboratory testing procedure Was also quantitative in nature and involved measurement of corrosion rates of metallic coupons. These were subjected to certain specific sets oftest conditions designedjto. approximate those found in. field operation which contribute to the corrosion. While it was obviously necessary to make some adjustments for small scale laboratory testing, a strong effort was made to incorporate those variables which are the major factors in causing corrosion in heat exchangers associated with cooling tower systems. The principal corrosive factors operating on the coupons are:

High dissolved oxygen level High chlorides, sulfates and total dissolved solids Low alkalinity, low pH (66.5

This test combined the advantages of both the batch type test and the once through test and was essentially an intermittent, once-through test. With this system, conditions were maintained constant throughout the test while a relatively small volume of water was used.

The equipment consisted of a series of individual units. Each unit was complete and independent of the others. It consisted of a five-gallon bottle which formed the reservoir for the test water. The water flowed from the reservoir by gravity to a feed assembly that controlled the head level. From there the water passed through a solenoid valve that was activated by an electrical timer. The timer opened the valve every eighteen minutes to allow 40 ml. of the water to flow into the test vessel that was partially immersed in a constant-temperature oil bath at 140 F. The rate of ilow was about 3.2 liters per day, corresponding to a 1.3 fold replacement of the water daily. The water left the test vessel through an overflow tube. The standard water used in this test had the same composition as the one used in Test Method A. Variations covering a range of typical cooling waters have been checked with results similar to those described here.

The test specimens were made of No. gauge SAE 1010 mild steel, and were one inch wide and 2 inches long. They were suspended in the test vessel from a inch hole drilled /4 inch for the short edge. The panels were prepared by sandblasting with flint shot sand. After sandblasting they were cleaned first in toluene and then in acetone, and weighed and placed in the test vessel. After the test they were removed and then cleaned by a second immersion in muriatic acid inhibited with formaldehyde. They were then removed from the acid and neutralized in a soda ash solution. The panels were then rinsed in water, dipped in acetone and air dried. Test panels were stored in a heated cabinet at 105 F. before weighing.

The test vessel was a Pyrex jar 6 inches in diameter and 8 inches tall, with an overflow tube at a point two inches from the top. The vessel was covered by a stainless steel lid that had a hole in the center to accommodate the stirrer, and holes around the edge for mounting the glass hook holders. The stirrer had a 1 inch by 2 inches paddle and rotated at 175 r.p.m. There were also holes in the lid to admit the tube from the reservoir, and an aerator. The tests were aerated continuously. These tests can be run for any length of time desired. Six coupons can be mounted in each test vessel. One was removed periodically to determine if the corrosion rates had leveled off. During the first few days of a test run the corrosion rates were relatively high and tended to be less reproducible, and for this reason it was necessary to run the test from 1530 days. The initial corrosion rate for the system with no inhibitor present was about 80 m.p.y. After an exposure of 15 days, the rate will reach equilibrium at about m.p.y.

Test method C.These tests were designed as a modification of test method B, and have a heat transfer surface which would act as a specimen for evaluation of corrosion and fouling. The test unit had a reservoir, feed system, and test vessel identical to those of test method B, except that no oil bath was used. Solution was pumped from the vessel by means of a centrifugal pump, then vertically through the annular space between a 17 inch long, /2 inch out diameter (O.D.), 16 gauge tube, and

cc./sec. 10- NRe Velocity (ft/sec.)

The coding water flow to the jacket was controlled by means of a thermostat in the test vessel, so that the vessel could be maintained at any desired temperature which, in these tests, was either or 160 F.

Using test method A, several of the quaternary ammonium salts in Table I were tested alone and in combination with sodium dichromate to determine their eifectiveness. These reuslts are presented below in Table II. The results were expressed in terms of P, F or G with the P indicating that the test material showed little or no activity, P meaning that it showed moderate activity, and G meaning that the material was good under the test conditions.

TABLE II Evaluation Test No. Description of test material Alone 1 CrO4 additive 2 2 heptadecenyl 1 (2 hvdroxethyD- 1 (4 chlorobutyl) imidazolinium chloride.

2 heptadecyl 1 (2 hydroxyethyD- l-benzyl imidazolinium chloride.

2 heptadecyl 1 (hydroxyethyl) 1- octadecyl imidazolinium ethyl sulfate.

Dodecyl trimethyl ammonium chlo- Hexadecyl trimethyl ammonium chlo- Octgdecyl trimethyl ammonium chlo- Coco trimeth vl ammonium chloride.. Soya trimethyl ammonium chloride Tallow trimethyl ammonium chloride Dicoco dimethyl ammonium chloride Coco amine Rx 15 moles EtO quaternizcd with methyl chloride. Octadecyl amine Rx 2 moles EtO quaternized with methyl chloride. Octadccenyl amine Rx 2 moles EtO qunternized with methyl chloride. Dihvdrogenated tallow d'unethyl ammonium chloride.

e e e e -s c e e e *1 *e Q Q QQQQ Q Q n 1 Using steel coupons, test material (200 ppm.) was evaluated as a corrosion inhibitor; pH 6.0-7.0; temperature F.

2 Using steel coupons, test material (40 ppm.) was evaluated as an additive to sodium dichromate- (40 ppm. Cr04) to reduce corrosion and pitting; pH 6.0-7.0; temperature 140 F.

I Free from rosin acid components.

To further evaluate the invention, test method B was employed. The tests were designed to determine more critically conditions favoring the use of various ingredients. The treatment and test results are given in Table 111.

TABLE 11 1- Evaluation of Chromate,-,Zinc Quaternqry Treqtments TREATMENT Gontinual, first week Remainder of run Quartemary in Analysis, p.p.m. in vessel, days .Composlreservoir (5 days) 7 Test tion N o. 7 N03 #0111 74 Table]; (304, Zn, Quat, 0x04, Zn, Quat, Theor. Actual 1 8 22 2S p,p,m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m.

1 A. Effect of Quat Concentration B. Effect of Zinc Ooncentrat-ion 12 7 so 2 so 2 2 2 12 I 30 4 2 30' 4 2 I 2 12 30 3 30 6 3 3 2.8 2.5 0.7 0.4. 1.0

'C. Efleet of Initial Chromate Slug in Vessel 12. 20 2 2o 4 2 2 2.0 2.4 1.9 0.6 1.0 12' 20 4 2 20 4 3 8 1. Q 1. 3 1. 6 0. 6 (1,9 12 20 2 20 2 2 z 1. 5. 0.9 1. 0' 0. 9'

' "DI Efie'ct'of Treatment Level E. Comparison on Active Dosage Basis 12 30 2 30 2 2 2. 0 I 1.0 1. 1 0.7 0. 8 19A 30 4 2 30 4 2 2 1. 9 4'. 2 0.8 O. 8 0.4 '8 30 2 30 4 2 2 0.5 1. 3 0. 1 O. 3 0.6

" F. Test without Quartemary 17 Blank 30 2 30 2 OBSERVATIONS AND RESULTS Tubemulation-pittlng evaluaiionfi days Overall film Cumulative corrosion, weight loss, mgs. Test formation Overall eon. 3. 7 rate, m.p.y.

1 s I 2 28 1 22 2s A. Effect of QuaLConcentration B. Efiect of Zinc Concentration 0. Effect of Initial Chromate Slug in Vessel D. Efieot of Treatment Level' E. Comparison on Active Dosage Basis F. Test without Qiiarternry "21241251 result.

employed in order to determine more completely the benefits of the inhibitors. These results are presented in 16 sorption was only a small fraction of the rate of loss by normal blowdown. Thus, the loss of quaternary to the wood in a cooling tower would be a factor during the ini- Table IV. tial treatment but this is counteracted by increasing the TABLE IV Evaluation of Chromate-Zinc-Quaternary Treatments Obtained With Heat Transfer Apparatus Pretreatment Follow-up treatment Observations on tube Quat. slug Quaternary (Table I) Test Type cnc., 01-0 Zn, period, Film Grease Tuberoulap.p.m. p.p.m. p.p.m. days formation removal tion Type p.p.m.

A. Blank none 40 4 14 Heavy.

B. Comparison of Quats on a Cost-Dosage Basis Quat Slug 40 30 6 3.0 8 Quat Slug 40 3O 6 19A 3. 9 8 Quat Slug 40 30 6 8 6.0 8

0. Effect of Initial Quat Concentration Quat Slug 40 30 6 12 5.0 Slight. Quat Slu 6O 3O 6 12 5.0 Do. Quat Slug SO 30 G 12 5. O Do. Quat Slug 60 3O 6 12 3.0 Mod. High Quat 60 2O 4 12 2.0 Trace Pretreatment Quaternary in Deposit analysis, mg. Weight data vessel, p.p.m.

Sca1e+ Quat. slug corr. Corr. Type c0110., 3 day 8 day PO; 0a Fe OR Quet. Zn prod.+ loss p.p.m. film,

A. Blank none 54 155 503 299 B Comparison of Quats on a Cost'Dosage Basis Quat Slug 40 1. 2 2. 3 22 203 8G Quat Slug 40 3. 3 4. 11 243 132 Quat Slug 40 2.1 1. 3 282 140 Quat Slug 96 16 0.2 2. 8 308 225 Quat Slug 15 2. 5 15 157 S1 Quat Slug 16 3.1 7 174 85 Quat Slug 31 0. 3 6 $7 a High Quat 61 0 58 1 Composition 12 of Table I used for slug in the test vessel at start of test. 2 32 p.p.m. OrOs, 6 p.p.m. Zn and 60 p.p.m. Comp. 12 for 4 days at 125 F.

To further illustrate the industrial utility of the in vention, a typical quaternary ammonium compound, octadecyl trimethyl ammonium chloride was tested to determine its rate of absorption on redwood, a material commonly used in cooling tower construction. The test method may be briefly described as follows:

Extracted redwood blocks were placed in contact with a volume of the quaternary ammonium salt solution such that the areazvolume ratio (34.5 sq. in.:1000 ml.) complied with the conditions of a typical cooling tower. In these tests the initial concentrations of the material were 20, 40, 80, and 120 p.p.m.; at intervals small samples (1% by volume) were Withdrawn for analysis. The results (Table V) show that initially roughly 20 p.p.m. of the quaternary ammonium salt is absorbed but that the rate drops off after a few hours. Although the salt continued to be absorbed for the next three weeks, the rate of ablevel of the initial high quaternary treatment. The results of these tests are presented in Table V below.

TABLE V Absorption of Oczadecyl T rimethyl Ammonium Chloride Concentration 01' compound found (p.p.m.) Time y 20 40 p.p.m. p.p.m. p.p.m. p.p.m

From Table II it will be observed that most of the quaternary ammonium salts tested were relatively inactive as inhibitors per se. When combined with the chromate, protection was afiforded.

An interesting result presented in Table III is the fact that when the system was initially treated, using a high dosage of quaternary ammonium salt, e.g., 40parts per million, and the lower concentration, viz., parts per million was maintained, better protection wasatforded than when the dosage of thev quaternary ammonium salt was held constant throughout the test, The reason for this phenomenon is believed to be that the initial high dosage. tends to form a protective coating on the surface which is subsequently maintained by the lower steady dosage.

Also observed from the results shown in Table III is that 40 parts per million of the quaternary ammonium salt, when maintained on a steady basis, is unnecessary once the protective coating is formed. The dosages from between 2 to 5 parts per million ofg the quaternary and from between 2 and 6 parts per million of the zinc salt give generally satisfactory, results It becomes evident from the above tests that one method of practicing the invention: is to feed relatively high dos ages of the quaternary ammonium salts to the system to form an initial protective film which is then subsequently maintained by the use of lower continual dosages. The amount of quaternary ammonium salt used to form this protective film, as well as the time in which it takesthe film to be formed, will, of course, be dependent upon the environmental factors present in each system. Thus, for instance, pH, temperature, dissolved solids, and the types of metals present must be taken into consideration. As a general rule, however, itmay be stated that the protective films may be morereadily formed. by using large dosages of the quaternary ammonium salts for short periods of time rather than using smaller dosages for long periods of time. In the case of a typical cooling tower system at least 40 parts per millon of the quaternary for at least 3 days should be used for forming the protective film.

The pretreatment with higher dosage quaternary ammonium salts provides a simple andefiiective method for stopping initial corrosion rates when industrial systems are first put on stream. It-will be understood, however, that the invention does not require such a pretreatment operation since in most cases a continual feed of the chemical at low economical dosages will eventually form an effective protective film that will be self-maintaining.

As a further guide to forming aninitial protective. film of the quaternary ammonium salt, the pretreatment of the system should employ from 20 to- 60 parts per millionand preferably 30 to 40 parts per million of the quaternary salt for a period of time ranging from 7 hours to 30 days. Quite frequentlyonly several days are required. The pretreatment is conducted using the same amountof chromate and heavymetal as previously specified.

In the specification, EtO is an abbreviation for ethyl-. ene oxide. Thus, in Table II, a test material coco amine Rx moles EtO quaternized' with methyl chloriderefers to an aminederived from coconut oil which has been oxyalkylated with 15 molesof ethylene oxide per mole of amine and then reacted with one mole, of methylene chloride per mole of amine.

The invention is hereby claimed asfollows:

1. A non-corrosive industrial process water which comprises a major portion of water, at least 10 parts per million of a water soluble hexavalent compound of chromium, calculated as CrO and at least 0.5 part per million of a water dispersible quaternary ammonium salt which contains at least one acyclic organic radical having at least 8 carbon atoms, the pH of said. water being within the range of 5.5 to 8.5

2. A non-corrosive industrial process water which comprises a major portion of water, 10 to 200 parts per million of a water soluble hexavalent compound of chromium, calculated as CrO and 0.5 to 10 parts per million 12 of a water dispersible quaternary ammonium salt which has at least one acyclic organic radical of at least 12 carbon atoms in chain length, the pH of said water being within the range of 5.5 to 8.5. i

3. A non-corrosive industrial process water which comprises a major portion of water, 10 to 200 parts per million of an alkali metal chromate, calculated as C10 and 0.5 to 10 parts per million of a water dispersible quaternary ammonium halide which contains one acyclic organic radical of at least 16 carbon atoms in chain length, the pH of said water being within the range of 5 .5 to 8.5.

4. A non-corrosive industrial process water which comprises a major portion of water, from 10 to 200 parts per million of an alkali metal chromate, calculated as Cr0 and from 0.5 to 10 parts per million of a water dispersible quaternary ammonium chloride of the formula R1 Cl.-

where R, is. a higher aliphatic group of from 1.6 to 18 carbon atoms inchain length and R R and R are lower aliphatic hydrocarbon groups having from 1 to 6 carbon atoms, the pH of said water being within the range of 6.5 to 7.5.

5. The non-corrosive industrial process water of claim 4 where the Water dispersible quaternary ammonium chromate is octadecyl trimethyl ammonium chloride.

6. A non-corrosive industrial process water which comprises a major portion of water, at least 10 parts per million of a water soluble hexavalent compound of chromium, calculated as CrO at least 0.5 part per million of a water dispersible quaternary ammonium salt which contains at least 8 carbon. atoms in, an acyclic chain and at least 0.25 part per million of an ionizable compound having a cationic heavy metal radical from the group consisting of zinc, cobalt, nickel, mercury and trivalent chromium, the pH of said water being within the range of 5.5 to 8.5.

7. A non-corrosive industrial process water which comprises a major portion of water, at least 10 parts per million of a water soluble hexavalent compound of chromium, calculated as CrO at least 0.5 part per million of a water dispersible quaternary ammonium salt which has at least one acyclic organic radical of at least 12 carbon atoms in chain length, and at least 0.25 part per million of an ionizable compound having a cationic heavy metal radical from the group consisting of zinc, cobalt, nickel, mercury and trivalent chromium, the pH of said water being within the range of 5.5 to 8.5.

8. A non-corrosive industrial process water which comprises a major portion of water, at least 10 parts per million of an alkali metal chromate, calculated as CrO at least 0.5 part per million of awater dispersible quaternary ammonium halide which contains one acyclic organic radical of at least 16 carbon atoms in chain length and from 0.2 5 to 6 parts per million of an ionizable compound having a cationic heavy metal radical from the group consisting of zinc, cobalt, nickel, mercury and trivalent chromium, the-pH of said water being withinv the range of 5 .5 to 8.5.

9. A non-corrosive industrial process water which comprises a major portion of water, from 10 to 200 parts per million of an alkali metal chromate, calculated as CrO from 0.5 to 10 parts per million of a water dispersible quaternary ammonium chloride of the formula Where R is a higher aliphatic group of from 16 to 18 carbon atoms in chain length and R R and R are lower aliphatic hydrocarbon groups having from 2 to 6 carbon atoms, and from 2 to 6 parts per million of an ionizable compound having a cationic heavy metal radical from the group consisting of zinc, cobalt, nickel, mercury andtrii3 valent chromium, the pH of said water being within the range of from 6.5 to 7.5.

10. The non-corrosive industrial process water of claim 9 wherein the water dispersible quaternary ammonium chloride is octadecyl trimethyl ammonium chloride and the ionizable compound of the heavy metal has a cationic zinc radical.

11. The non-corrosive industrial process water of claim 9 which also contains from 0.5 to 2 parts per million of a molecularly dehydrated phosphate, calculated as P 12. The process of protecting metals against corros on by contact with aqueous liquids which comprises feeding from separate supply sources into an aqueous industrial process water having a pH within the range of 5.5 to 8.5, an amount of a water soluble hexavalent compound of chromium calculated as C suflicient to provide in said water at least 10 parts per million thereof, and an amount of a water dispersible quaternary ammonium salt sufficient to provide from 20 to 60 parts per million thereof in said water, said quaternary ammonium salt having at least one acyclic organic radical with at least 8 carbon atoms, contacting the metals of an aqueous process system with said water subsequent to said feeding, for a period of time ranging from 7 hours to 30 days sutiicient to establish a protective film on said metals, and then continuing to treat said metals with said water while maintaining feeding of said quaternary salt in amounts sufficient to maintain said protective film.

13. The process of claim 12 wherein feeding is sufficient to provide in said water from 10 to 200 parts per million of a water soluble hexavalent compound of chromium, and 0.5 to 10 parts per million of a water dispersible quaternary ammonium salt, and wherein the said quaternary ammonium salt has at least one acyclic organic radical of at least 12 carbon atoms in chain length.

14. The process of claim 13 wherein the water soluble hexavalent compound of chromium is an alkali metal chromate and the water di'spersible quaternary ammonium salt is a quaternary ammonium halide having one acyclic organic radical of at least 16 carbon atoms in chain length.

15. The process of claim 14 wherein the quaternary ammonium halide has the formula:

where R is a higher aliphatic group of from 16 to 18 carbon atoms in chain length and R R and R are lower aliphatic hydrocarbon groups having from 1 to 6 carbon atoms.

16. The process of claim wherein the quaternary ammonium halide is octadecyl trimethyl ammonium chloride.

17. The process of protecting metals against corrosion by contact with aqueous liquids which comprises feeding from separate supply sources into an aqueous industrial process water having a pH within the range of 5.5 to 8.5, an amount of a water soluble hexavalent compound of chromium calculated as CrO sufficient to provide in said Water at least 10 parts per million thereof, and an amount of a water dispersible quaternary ammonium salt sulficient to provide from 20 to 60 parts per million thereof in said water, and also feeding into said Water from a supply source in an amount sufiicient to provide in said water at least 0.25 part per million of an ionizable compound having a cationic heavy metal radical from the group consisting of zinc, cobalt, nickel, mercury and trivalent chromium, said quaternary ammonium salt having at least one acyclic organic radical with at least 8 carbon atoms, contacting the metals of an aqueous process system with said water subsequent to said feeding for a period of time ranging from 7 hours to 30 days sufiicicnt to establish a protective film on said metals, and then continuing to treat said metals with said water while maintaining feeding of said quaternary salt in amounts sufiicient to maintain said protective film.

18. The process of claim 17 wherein the quaternary ammonium salt has at least one acyclic organic radical of at least 12 carbon atoms in chain length.

19. The process of claim 18 wherein the quaternary ammonium salt is a quaternary ammonium halide containing one acyclic organic radical of at least 16 carbon atoms in chain length, and wherein feeding is sufiicient to provide in said water from 0.25 to 6 parts per million 2 said ionizable compound having a cationic heavy metal radical.

20. The process of claim 19 wherein the quaternary ammonium halide has the formula:

in where R is a higher aliphatic group of from 16 to 18 carbon atoms in chain length and R R and R are lower aliphatic hydrocarbon groups having from 1 to 6 carbon atoms, and wherein feeding is sufiicient to provide in said water 2 to 6 parts per million of said ionizable com pound having a. cationic heavy metal radical, and wherein the pH of said water is Within the range of from 6.5 to 7.5.

21. The process of claim 20 wherein the quaternary ammonium chloride is octadecyl trimethyl ammonium chloride and the ionizable compound of a heavy metal has a cationic zinc radical.

22. The process of claim 21 wherein feeding is further maintained sufiicient to provide in said water from 0.5 to 2 parts per million of a. molecularly dehydrated phosphate, calculated as P0 References (Iited in the file of this patent UNlTED STATES PATENTS 2,274,058 Goebel et al. Feb. 24, 1942 2,325,359 Arnold et al July 27, 1943 2,711,391 Kahler June 21, 1955 2,738,325 Rydell Mar. 13, 1956 2,793,932 Kahler et al. May 28, 1957 2,872,281 Kahler et a1. "Feb. 3, 1959 2,877,085 George et al Mar. 10, 1959 2,900,222 Kahler et a1. Aug. 18, 1959 2,947,703 Larsonneur Aug. 2, 1960 UNITED STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Patent No 3,079,220, February 26,, 1963 David B. Boies et a1.

ppears in the above numbered pet- It is hereby certified that error 51 id Letters Patent should read as ent requiring correction and that the se corrected below.

Column 12, line 72, for "2" read 1 Signed and sealed this 17th day of December 1963.

Attest:

(SEAL) EDWIN E. REYNOLDS ERNEST w. SWIDER I v Commissioner of Patents Attesting Officer

Claims

12. THE PROCESS OF PROTECTING METALS AGAINST CORROSION BY CONTACT WITH AQUEOUS LIQUIDS WHICH COMPRISES FEEDING FROM SEPARATE SUPPLY SOURCES INTO AN AQUEOUS INDUSTRIAL PROCESS WATER HAVING A PH WITHIN THE RANGE OF 5.5 TO 8.5, AN AMOUNT OF A WATER SOLUBLE HEXAVALENT COMPOUND OF CHROMIUM CALCULATED AS CRO4 SUFFICIENT TO PROVIDE IN SAID WATER AT LEAST 10 PARTS PER MILLION THEREOF, AND AN AMOUNT OF A WATER DISPERSIBLE QUATERNARY AMMONIUM SALT SUFFICIENT TO PROVIDE FROM 20 TO 60 PARTS PER MILLION THEREOF IN SAID WATER, SAID QUATERNARY AMMONIUM SALT HAVING AT LEAST ONE ACYCLIC ORGANIC RADICAL WITH AT LEAST 8 CARBON ATOMS, CONTACTING THE METALS OF AN AQUEOUS PROCESS SYSTEM WITH SAID WATER SUBSEQUENT TO SAID FEEDING, FOR A PERIOD OF TIME RANGING FROM 7 HOURS TO 30 DAYS SUFFICIENT TO ESTABLISH A PROTECTIVE FILM ON SAID METALS, AND THEN CONTINUING TO TREAT SAID METALS WITH SAID WATER WHILE MAINTAINING FEEDING OF SAID QUATERNARY SALT IN AMOUNTS SUFFICIENT TO MAINTAIN SAID PROTECTIVE FILM.