WO2001051584A1

WO2001051584A1 - Deicing compositions and methods of use

Info

Publication number: WO2001051584A1
Application number: PCT/US2001/000853
Authority: WO
Inventors: Kris A. Berglund; Hasan Alizadeh; Dilum D. Dunuwila
Original assignee: Applied Carbo-Chemicals; Michigan State University
Priority date: 2000-01-11
Filing date: 2001-01-10
Publication date: 2001-07-19
Also published as: RU2222564C1; AU2001234437A1; EP1254195A4; US6287480B1; CA2396054C; CA2396054A1; EP1254195A1; RU2002118696A

Abstract

Improved deicing compositions and methods are provided. The invention is directed to deicing compositions which are substantially less corrosive than allowed for use on aircraft metal parts. The subject invention is also directed at deicing compositions which inhibit the corrosive effects of conventional road salt. The inventive deicing compositions comprise effective deicing amounts of succinate salts, such as potassium succinate (trihydrate), ammonium succinate (anhydrous), sodium succinate (hexahydrate), either alone or in combination. Figure 1 is a graph depicting the ice penetration performance of potassium succinate (present invention) and CMA (a conventional road salt).

Description

DEICING COMPOSITIONS AND METHODS OF USE

BACKGROUND OF THE INVENTION

The invention relates generally to a deicing composition and method of

using the same and more particularly, to a deicing composition comprising succinate salts

and methods of using succinate salt compositions for deicing applications at airport

facilities and other applications involving specialty materials as well as for highway,

residential and commercial deicing.

Chemical deicing is routinely used during the winter season to maintain

safer mobility on United States highways and airports. There are numerous materials and

compositions presently used for such deicing applications. However, there are many

disadvantages to the presently used materials, including their corrosiveness, cost and their

impact on the environment.

Common road salt is the most widely used deicing chemical on highways,

driveways, sidewalks, etc. It is generally effective, inexpensive, reliable and easy to store

and apply. As described in "Highway Deicing: Comparing Salt and Calcium Magnesium

Acetate^", Special Report 235, Transportation Research Board Committee on the

Comparative Costs of Rock Salt and CMA for Highway Deicing, Washington, D.C.,

(1991), incorporated herein by reference, an estimated 10 million tons of road salt, at

$35/ton, is used each year.

One'of the major problems with road salt is that due to its corrosiveness. It

has the potential to cause costly damage to highway infrastructure, driveway and sidewalk surfaces, motor vehicles and the environment. Structural damage may include concrete

degradation and steel corrosion, which generally leads to high maintenance expenditure.

Foliage burns, soil compaction and water contamination are some of the adverse

environmental manifestations of sodium chloride use.

As described in, W. L. Miller, "Ways to Help Bridges and Deicers Coexist:

CMA Cuts Corrosion on Zilwaukee Bridge , Better Roads, (February, 1993), and R.

Strawn, "CMA has Role to Play in Critical Applications^", T. Kuennen, Ed., Roads &

Bridges, (March, 1993), each of which is hereby incorporated by reference, due to the

problems associated with the corrosiveness of generally used salts as road deicing

chemicals, a less harmful road deicing chemical, namely calcium magnesium acetate

(CMA) was commercialized. Calcium magnesium acetate is known to inhibit concrete

degradation and corrosion. It is also known to be less harmful to the environmental than

conventional road salt. However, one of the downsides of CMA is its cost, which at

$925/ton, is 20 times as much as common road salt. Further, CMA is a less than fully

satisfactory deicer.

ICE BAN^® is a recently developed deicer composition available from Ice

Ban America, Inc. As described at the company's web site, http://www.iceban.com, ICE

BAN^® is a natural liquid concentrate residue from the wet milling of corn and the

production of alcohol. It is generally non-corrosive and has good anti-icing and deicing

properties. However, this product has not proved to be fully satisfactory. One downside

of ICE BAN^® is that it is formulated as a liquid deicer. Equipment currently used for spreading of conventional deicers are configured for solid deicers. Switching to a liquid

deicer would require expensive equipment reconfigurations, leading to significant capital

investment in addition to the capital required for liquid storage tanks. The viscosity of the

liquid at low temperatures can pose additional problems.

Another currently available deicer is known as CF7, which is based on

potassium acetate, manufactured by CRYOTECH, and which is believed to be scheduled

for testing at airport applications. Airport and airbase deicers need to comply with

stringent criteria and standards. It is believed that CF7 may pose corrosion problems in

connection with certain airport applications and thus may not comply with standards for

deicing aircraft metals.

EP Publication No. 0 077 767 discloses, inter alia, discloses a dicarboxylic

acid mixture (hereinafter "DAM") consisting of adipic acid (30-35 %wt), glutaric acid

(40-50 %wt) and succinic acid (20-25 %wt) in the form of a potash salt which is asserted

to be suitable for airport deicing. This formulation is in liquid form and is believed to

possess deicing characteristics. However, it is believed that it does not comply with the

corrosion standard for aircraft metals, and, in particular, does not comply with the

corrosion standards for dichromate treated magnesium, which is the aircraft metal alloy

that is most susceptible to corrosion.

The reference also discloses a combination of potassium salt of pure

succinic acid, urea and water as an anti-freeze solvent (35.5 parts by weight: 25 part: 41.5

parts). The reference also states that the use of pure potassium succinate was less favorable as an antifreeze and corrosion inhibitor than the dicarboxylic acid mixtures

disclosed therein, clearly discouraging use of potassium succinate in favor of a mix of

certain carboxylic acids. Sixteen years have passed since this application was published

and no commercial product based on the disclosure therein has gained any measure of

market acceptance.

Thus, it is desirable to provide an improved deicing composition and

method of using the same which is more commercially viable than those which have been

suggested in the past.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the invention, improved deicing

compositions and methods are provided. In particular, the subject invention is directed at

deicing compositions which are suitable and effective for airport applications in which

corrosion of magnesium based alloys is an issue. The present invention provides deicing

compositions which can provide improved ice penetration characteristics and in

particular, which can provide improved ice penetration characteristics compared to CMA,

while maintaining relatively benign environmental effects. Further, the subject invention

is directed at deicing compositions which can penetrate ice at temperatures below about -

10°C.

The subject invention is also directed at deicing compositions which are

less corrosive than conventional road salt. In particular, the invention is directed at

deicing compositions which are less corrosive of steel and aluminum and certain magnesium based parts than conventional road salt. For example, the invention is

directed to deicing compositions which are substantially less corrosive than allowed for

use on aircraft metal parts, such as magnesium based alloys.

The subject invention is also directed at deicing compositions which inhibit

the corrosive effects of conventional road salt. In particular, the invention is directed at

deicing compositions which inhibit road salt corrosion of steel and aluminum and deicing

compositions which inhibit corrosion of dichromate treated magnesium alloys and other

aircraft metal alloys, as commonly used in airport/aircraft facilities or equipment.

The subject invention is also directed at deicing compositions comprising

effective deicing amounts of succinate salts, such as potassium succinate (trihydrate),

ammonium succinate (anyhdrous), sodium succinate (hexahydrate), either alone or in

combination. The subject invention is also directed at deicing compositions comprising

effective corrosion inhibiting, deicing amounts of potassium succinate together with

effective amounts of either 1) polymaleimide sodium salt and magnesium succinate, 2)

magnesium succinate and sodium polyaspartate, 3) polymaleimide sodium salt 4) sodium

polyaspartate and polymaleimide sodium salt, 5) magnesium succinate or 6) sodium

chloride which will enhance deicing and/or corrosion inhibiting properties. The subject

invention is also directed at deicing compositions comprising sodium chloride together

with an effective amount of succinate salts, such as potassium succinate for deicing with

enhanced corrosion inhibiting properties. In accordance with a preferred embodiment of the present invention, the

subject invention is also directed at a deicing composition comprising an effective amount

of ammonium succinate for enhanced deicing and corrosion inhibition.

The subject invention is also directed to compositions for inhibiting the

corrosive effects of conventional road salt comprising a deicing and corrosion inhibiting

effective amount of succinate salts, and in particular, either potassium succinate

(trihydrate), ammonium succinate (anyhdrous) or sodium succinate (hexahydrate), either

alone or in combination with each other.

The subject invention is also directed to compositions for inhibiting the

corrosive effects of conventional road salt comprising combining sodium chloride with an

effective amount of either potassium succinate, ammonium succinate, sodium succinate,

sodium polyaspartate or polymaleimide sodium salt, either alone or in combination with

each other to reduce the corrosive properties of a composition with sodium chloride.

In accordance with a preferred embodiment of the present invention, the

subject invention is also directed at compositions for inhibiting the corrosive effects of

conventional road salt comprising combining sodium chloride with an effective amount

of sodium succinate and sodium polyaspartate to reduce the corrosiveness of the

composition.

In accordance with a preferred embodiment of the present invention, the

subject invention is also directed at methods of deicing surfaces, materials or articles,

such as an airport runway or airport equipment comprising applying a composition comprising an effective deicing amount of potassium succinate and other optional

activities to the surface, material or article.

In accordance with a preferred embodiment of the present invention, the

subject invention is also directed at methods of deicing an aircraft comprising the step of

applying a composition comprising an effective amount of potassium succinate to the

aircraft, runway or other airport objects.

The invention accordingly comprises the several steps and the relation of

one or more of such steps with respect to each of the others, and the compositions

possessing the characteristics, properties and the relation of constituents useful to effect

such steps, which will be exemplified in the compositions hereinafter described, all as

exemplified in the following detailed disclosure, and the scope of the invention will be

indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to the following

description taken in connection with the accompanying drawings, in which:

Figure 1 is a graph depicting the ice penetration performance of potassium

succinate and CMA at different temperatures;

Figure 2 is a graph depicting the rate of steel corrosion in aqueous deicer

solutions containing 3 %wt deicer;

Figure 3 is a graph depicting the ice penetration performance of succinate

salts in comparison to road salt at different temperatures; Figure 4 is a graph depicting the ice penetration performance of 50:50

succinate mixtures compared to potassium succinate;

Figure 5 is a graph depicting the rate of steel corrosion in aqueous deicer

solutions containing 3 %wt deicer;

Figure 6 is a graph depicting the rate of aluminum corrosion in aqueous

deicer solutions containing 3 %wt deicer;

Figure 7 is a graph depicting the rate of steel corrosion in aqueous solutions

containing 3 %wt deicer;

Figure 8 is a graph depicting the rate of steel corrosion in aqueous solutions

containing 3 %wt deicer (sodium polyaspartate:sodium chloride);

Figure 9 is a graph depicting the rate of steel corrosion in aqueous solutions

containing 3 %wt deicer (sodium succinate:sodium polyaspartate:sodium chloride);

Figure 10 is a graph depicting the rate of steel corrosion in aqueous deicer

solutions containing 3 %wt deicer;

Figure 11 is a graph depicting the rate of dichromate treated magnesium

alloy corrosion in aqueous deicer solutions containing 3 %wt deicer, except in the case of

"a" where CF7 was used as received;

Figure 12 is a graph depicting the rate of dichromate treated magnesium

alloy corrosion in aqueous solutions containing 3 %wt deicer (potassium

succinate:sodium polyaspartate); Figure 13 is a graph depicting the rate of dichromate treated magnesium

alloy corrosion in aqueous solutions containing 3 %wt deicer;

Figure 14 is a graph depicting the freezing point depression of 50 %wt

aqueous deicer solutions; and

Figure 15 is a graph depicting scaling of concrete specimens in different

solutions and water after 5 to 50 freezing/thawing cycles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The subject invention is directed at deicing compositions, including those

comprising succinate salts and methods of use. Succinate salts are naturally occurring as

well as being genetically manufacturable according to, for example, application Ser. No.

09/134,061 and Pat. No. 5,770,435, the contents of which are incorporated herein by

reference. When used herein, the term succinate salts refers to either the naturally

occurring salts, those synthetically produced or those produced via genetic engineering.

However, methods involving genetically engineered salts can provide significant

advantages, particularly in providing the salts at particularly advantageous prices.

Applicants determined that potassium succinate (e.g., potassium succinate

trihydrate) repeatedly outperformed other succinate salts. It was found to be an effective

deicer and non-corrosive. In comparison to CMA, the use of potassium succinate may

result in up to a 40% direct savings. Additional indirect savings could be realized on

account of the superior deicing capability of potassium succinate. Considering the

financial burden incurred by State and County road authorities due to steel corrosion and concrete loss directly as a consequence of road salt use, potassium succinate should prove

to be a cost effective, non-corrosive deicer for many of the expensive highway structures.

In addition, it may be a viable option for application on environmentally sensitive areas

where loss of vegetation and habitat is a concern. As a deicer that is superior in

performance to CMA, potassium succinate will find a place in niche markets as has

CMA.

Airport and airbase deicing is another extremely viable market for

potassium succinate based deicers. Airport and airbase deicers need to comply with

stringent criteria. These criteria are set to protect specialty alloys used in aircrafts in

structurally critical areas. Applicants determined that potassium succinate can be

formulated to meet and even far exceed the standard corrosivity requirements for aircraft

metals. The potential for a potassium succinate based deicer for applications in airports

and airbases is enormous. Although, material cost is always a driving factor in any

application, the savings on service and repair expenditure that could be realized as a result

of using a non-corrosive deicer is very likely to render the use of potassium succinate in

such high-end applications economically feasible.

To establish that succinate salts are effective deicers, the ice penetrating

capabilities of succinate salts were compared with other deicers. Also, due to the

stringent criteria for airport deicers, the corrosiveness and corrosive inhibiting effects of

succinate salts as compared with other deicers were established. It was determined that many chloride blends containing succinate or

succinate derived corrosion inhibitors displayed performance characteristics that were

highly advantageous toward highway deicing. The tested inhibitors were capable of

suppressing corrosion induced by the chloride salts as much as 50-75 %. This corrosion

suppression is advantageous because blends composed of high sodium chloride levels

will assist in the development of an affordable product for road deicing applications. In

addition, the presence of corrosion inhibitors in small quantities were not found to

attenuate the ice-penetration and ice-melting capacities of chloride salts. The net result is

a family of cost effective, high-performance deicers that are substantially less corrosive

than straight chloride salts.

One notable determination was that potassium succinate based deicer

formulae are ideally suited for airport and airbase deicing applications. Airport and

airbase deicers need to comply with stringent corrosion criteria. These criteria are set to

protect the specialty alloys used in aircrafts. It has been found that potassium succinate

and other succinates in combination with carboxylate derived polymeric corrosion

inhibitors exhibit tremendous success in formulating non-corrosive potassium succinate

based deicers for application in airports and airbases. Neither CF7 nor DAM that have

been formulated for airport deicing complied with standards for aircraft metal corrosion.

It was determined that potassium succinate repeatedly outperformed other

succinate salts. It is an effective deicer and it is non-corrosive. The different tests and

experiments conducted by applicants are described below. Aspects of the invention will be discussed and exemplified with reference

to the following examples which are presented for illustrative purposes only and are not

intended to be construed in a limiting sense.

Method For The Determination Of Ice-Penetrating Capacity Of Deicers

As described below, a slightly modified version of the SHRP H-205.3

protocol of the "Handbook of Test Methods for Evaluating Chemical Deicers , SHRP-

H/WP-90, Strategic Highway Research Program, National Science Counsel, Washington,

D.C., (1992) , incorporated herein by reference, was followed. The ice-penetration

capacity was measured based on an observation of the penetration behavior of the deicer,

which occurs chiefly by the propagation of a uniform melt front downward through the

ice. The test involved the following steps:

1. Distilled water was placed in standard ice-penetration test cells and frozen.

2. Deicer samples of 25 mg or 100 mg were stored at room temperature.

3. The deicers were placed on the ice in the test cell at preset temperatures of

-5 °C, -10 °C, -15 °C and -20 °C.

4. At regular intervals of 10, 20, 30, 45 and 60 minutes, the ice-penetration

depth was measured. The penetration depth was observed with the aid of a

drop of dilute Bulls-Eye^® dye placed on the ice surface. The dye gives a

distinctive blue color at the ice-penetration front.

5. Tests were performed in triplicate.

Method For The Determination Of Steel And Aluminum Corrosion Properties The evaluation of corrosion inhibition properties, the SHRP H-205.7

protocol of the "Handbook of Methods for Evaluating Chemical Deicers", incorporated

herein by reference, was followed. Corrosion properties of the numerous deicers were

evaluated using 3 %wt aqueous solutions. The test protocol involved the following steps;

1. Seven hundred and fifty milliliters of aqueous salt solutions was placed in

stoppered Erlenmeyer flasks. The stopper was intended to prevent the rapid

evaporation of water while permitting aeration for accelerated corrosion

under controlled conditions. Metal coupons (SAE 1010 steel and ASTM

D1730 aluminum), 1 x 2 , were suspended in the solutions with the aid of

nylon string tied to a hole in the coupon.

2. The metal coupons were subjected to accelerated corrosion for two weeks

while monitoring airflow, solution level, solution color and solution pH.

3. The corrosion rate, in mpy (1/1000 inches per year), was determined using

the SHRP H-205.7 protocol for steel and aluminum.

Method For The Determination Of Magnesium Corrosion Properties

For the evaluation of corrosion inhibition properties the ASTM F 483-91

protocol of the "Standard Test Method for Total Immersion Corrosion Test for Aircraft

Maintenance Chemicals", incorporated herein by reference, was followed. Corrosion

properties of the numerous deicers were evaluated using 3 %wt aqueous solution. The

test protocol involved the following steps; 1. 450 milliliters of aqueous salt solutions were placed in stoppered

Erlenmeyer flasks. The stopper was intended to prevent the rapid

evaporation of water. The solutions were kept at 38 °C during 24 hours of

experimentation. Metal coupons (Dichromate treated as in AMS 2475

Wrought Magnesium alloy designated as ASTM AZ31B to AMS 4376.),

1 x2 , were suspended in the solutions with the aid of nylon string tied to a

hole in the coupons.

2. The metal coupons were subjected to corrosion for 24 hours while

monitoring solution level, temperature, color and pH.

3. The corrosion rate, expressed in mg/cm , was determined using ASTM F

483-91 protocol.

Method For The Determination Freezing Points

The following protocol was followed to determine the freezing points of deicers.

Deicer concentration in aqueous media was 50 %wt.

1. Eight milliliters of aqueous deicer solutions were placed in sealed, plastic

tubes.

2. The tubes were immersed overnight in a Polystat Chiller containing silicone

heat transfer fluid maintained at pre-determined temperatures. The

temperature range was 0 to -45 °C.

3. After the overnight immersion period, the deicer samples were visually

examined to identify the frozen ones and recorded. 4. The temperature was further lowered and the samples remaining in a liquid

state were kept immersed overnight.

5. Steps 3 and 4 were repeated until all samples in an experiment were frozen.

Example 1

First, the performance of substantially pure solid potassium succinate was

compared to that of CMA to demonstrate the overall superiority of potassium succinate as

a non-corrosive deicer with respect to ice-penetration capacity and corrosion

characteristics.

The ice-penetration performance of potassium succinate and CMA are

presented in Figure 1. The protocol described earlier (Method For The Determination Of

Ice-Penetrating Capacity Of Deicers) was used with 25 mg of solid deicer. The rate of

ice-penetration of CMA at -5°C and -10°C is significantly lower than that of potassium

succinate. Calcium magnesium acetate was totally ineffective below -10°C. Clearly,

potassium succinate was shown to be a superior deicer compared to CMA at temperatures

down to -20°C and does not freeze until its temperature drops below -40°C.

Example 2

The steel corrosion rates in 3 %wt aqueous solutions of potassium

succinate, CMA and sodium chloride were evaluated. The results indicate that both

potassium succinate and CMA do not promote significant steel corrosion. The rate of

steel corrosion in potassium succinate and CMA was 0.01 mpy and 0.04 mpy,

respectively. These negligible values would fall into experimental error limits. This is confirmed by the observation that no corrosion appeared on metal samples in repeated

experiments. Conversely, the steel corrosion rate in sodium chloride was 18 mpy and

corrosion was visible.

Example 3

The inhibition of steel corrosion by potassium succinate and CMA in

aqueous sodium chloride solutions were evaluated. The added potassium succinate and

CMA was 2 %wt of the total amount of salt while the total amount of salt was 3 %wt of

the aqueous solution. The results of this experiment are presented in Figure 2. As shown,

small amounts of either potassium succinate or CMA have a significant impact on the

corrosiveness of sodium chloride. Both potassium succinate and CMA inhibited more

than 50% of the corrosion induced by sodium chloride.

Examples 1-3 were designed to compare the performance characteristics of

potassium succinate with that of CMA which is the most recognized commercially

available alternative highway deicer. The comparison criteria included ice-penetration

capacity, corrosion and corrosion inhibition properties. The rate of ice-penetration by

CMA was shown to be significantly slower than that by potassium succinate. CMA did

not penetrate ice below -10°C, whereas potassium succinate penetrated ice at

temperatures as low as -20°C and can exhibit deicing characteristics at still lower

temperatures.

Potassium succinate and CMA were shown to be non-corrosive and to

inhibit the corrosive tendencies of sodium chloride in excess of 50%. Both are biodegradable and should not have any cumulative effects on the environment. The

Federal Highway Administration ("FHWA") identifies CMA as the "only environmental

alternative to salt" at the present time. However, it has been determined that the deicing

capability of potassium succinate is superior to that of CMA while possessing essentially

the same environmental benefits and protection from corrosion that CMA provides. This

is in addition to a 40% savings on a direct cost basis. More savings can be realized due to

the superior deicing capability of potassium succinate. Savings will materialize as a

result of reduced application loads and frequencies. This suggests that potassium

succinate is a more viable alternative deicer for application on expensive road structures

and environmentally sensitive areas.

Example 4

The performance of potassium succinate was compared to that of other

succinate salts. The succinate salts included sodium, ammonium, calcium and

magnesium succinate.

The SHRP H-205.3 protocol of the "Handbook of Methods for Evaluating

Chemical Deicers" for evaluating ice-penetration capacity of deicing chemicals suggests

the use of 25 mg of deicer in a test cell. However, 100 mg of deicer was used based on

the respective anhydrous species to accentuate the subtleties, if any, in the performance of

the salts tested. Therefore, the absolute ice-penetration depths of potassium succinate

presented in Figure 1 differs from that presented in this Example. As shown in Figure 3, potassium succinate (trihydrate) repeatedly

outperformed all the other salts followed, by ammonium succinate (anhydrous) and

sodium succinate (hexahydrate) over the temperature range studied. Ice-penetration of

succinate salts was also compared to that of road salt. The final depth reached by

potassium succinate (trihydrate) was about half of that reached by road salt. Sodium

succinate (anhydrous), calcium succinate (monohydrate) and magnesium succinate

(anhydrous) were also tested. Sodium succinate (anhydrous) had minimal ice-penetration

capacity at -3°C and hardly any at lower temperatures. Calcium succinate had no deicing

capability. The deicing capability of magnesium succinate was negligible.

Example 5

The synergistic effects of these salts were also confirmed. Ice-penetration

tests were carried out using 50:50 mixtures of potassium succinate (trihydrate),

ammonium succinate (anhydrous) and sodium succinate (hexahydrate). The components

were measured on an anhydrous basis. The results are presented in Figure 4. At -3 °C,

the performance of all the mixtures was comparable to that of essentially pure potassium

succinate (trihydrate). However, at lower temperatures, the ice-penetration capacities of

the mixtures diminished dramatically in comparison to that of essentially pure potassium

succinate (trihydrate). Overall, there was no evidence of synergistic behavior. In fact,

mixing seemed to attenuate the deicing power of both potassium and ammonium

succinate. The data obtained suggest that potassium succinate possesses the best ice-

penetration capacity. In high-end applications, such as airport/airbase deicing, where

high costs on services and repairs attributed to the use of inferior deicers override the

need for very cheap deicers, potassium succinate has been shown to be a viable

alternative. Potassium succinate based deicing formulae that comply with the stringent

standards for airport/airbase deicers are presented and discussed in Examples 10 and 13.

Example 6

The steel corrosion rate in 3 %wt aqueous solutions of potassium succinate,

sodium succinate, ammonium succinate and sodium chloride was studied. The results

presented in Figure 5 indicate that the succinate salts, with the exception of ammonium

succinate, do not promote steel corrosion. The rate of steel corrosion in potassium

succinate and sodium succinate was 0.01 mpy and 0.03 mpy, respectively. Therefore, the

values are not visible on the chart. It is believed that these negligible values would fall

into experimental error limits. This is confirmed by the observation that no corrosion

appeared on metal samples in repeated experiments. The steel corrosion rate in sodium

chloride was 18.

The SHRP H-205.7 protocol of the "Handbook of Methods for Evaluating

Chemical Deicers" that was used to evaluate corrosion properties of the salts, calls for the

suspension of two steel coupons in aqueous deicer solutions. The electrochemical

properties of ammonium succinate facilitate extensive corrosion of one of the coupons

and protect the other from any corrosion. Ammonium succinate displayed this behavior in repeated experiments. The method used by the protocol to report the data is the

average rate of corrosion of the two suspended coupons. For ammonium succinate, the

average, as given in Figure 5, is 17.13 mpy. This average corrosion rate is reflective of

one steel coupon that corroded as much as 34.26 mpy and one that corroded 0.0 mpy.

The aluminum corrosion rate in 3 %wt aqueous solutions of potassium

succinate, sodium succinate, ammonium succinate and sodium chloride was studied and

the results are presented in Figure 6. The results indicate that both potassium succinate

and sodium succinate do not promote aluminum corrosion. The rate of aluminum

corrosion in potassium succinate and sodium succinate was 0.00 mpy and 0.05 mpy,

respectively. These negligible values, are believed to fall into experimental error limits.

This is confirmed by the observation that no corrosion appeared on metal samples in

repeated experiments. Conversely, the aluminum corrosion rate in sodium chloride was

5.4 mpy. The rate of aluminum corrosion in ammonium succinate solutions was 0.5 mpy.

Although aluminum corrosion rate in ammonium succinate solutions is higher than that in

potassium and sodium succinate solutions, it is substantially lower than that in sodium

chloride solutions.

Example 7

The inhibition of steel corrosion by potassium succinate, sodium succinate

and ammonium succinate in aqueous sodium chloride solutions was studied. The amount

of succinate in the chloride blends was 2% by weight (%wt) of deicer. The aggregate amount of deicer was 3 %wt of the aqueous solution. Results of these experiments are

presented in Figure 7

All three succinates displayed inhibition of chloride induced corrosion in

excess of 50%. Thus, formulations inhibiting corrosion by at least 20% or higher (or

lower, for that matter) are also possible. This data suggests that the succinates possess

corrosion inhibition capabilities in addition to being non-corrosive.

Example 8

The impact of alternative corrosion inhibitors that can be derived

economically from carboxylic acids, such as succinic acid and maleic acid with potential

for use in combination with succinate deicers was investigated. Two polycarboxylates, a

sodium polyaspartate sold by Bayer and a polymaleimide sodium salt have been

experimented with. In this regard, applicants were primarily interested in studying

possible synergistic enhancements of corrosion inhibition by combinations of succinates

and polycarboxylates.

Applicants investigated the effect of sodium polyaspartate on steel

corrosion induced by sodium chloride. The results are presented in Figure 8. All the

compositions studied display inhibition of corrosion in excess of 50%. Thus, formulations

inhibiting corrosion less than 50%, such as at least 20% can also be formulated. One

observed feature was that it is equally effective at very low levels (sodium polyaspartate :

sodium chloride = 0.1:99.9). Effectiveness at low levels is a promising prospect since it will aid in reducing the cost of the deicer to be competitive in low-end applications such

as highway deicing.

Example 9

Possible synergistic enhancement of corrosion inhibition by mixtures of

succinates and polyaspartate was investigated. Results of experiments carried out with

sodium succinate and sodium polyaspartate are given in Figure 9. The results suggest that

the 4.0:1.0:95.0 ratio of sodium succinate/sodium polyaspartate/sodium chloride

contributed to an enhancement in corrosion inhibition. The amount of corrosion allowed

by this composition is less than allowed by any of the succinate and chloride blends.

Experiments were conducted to confirm the effect of the polymaleimide

sodium salt on steel corrosion induced by sodium chloride. The results are presented in

Figure 10. The data indicate that the polymaleimide sodium salt is capable of inhibiting

75% of the corrosion induced by sodium chloride. With regard to aqueous sodium

chloride solutions, this is the most inhibition realized in the experiments with high sodium

chloride content. The data also indicate that the amount of inhibition provided by the

polymaleimide sodium salt are dependent on its chemical makeup.

It is believed that 75% less corrosive sodium chloride and calcium chloride

based deicers will find a place in many deicing applications regardless of the slight

increase in cost resulting from the inclusion of a small amount of inhibitor. The accrued

savings due to the anticipated reduction in repair and service costs associated with corrosion is believed to easily override the additional up-front costs leading to net

savings.

Example 10

The data established that potassium succinate is ideally suited for deicing

ahports and airbases. Aiφort and airbase deicers have to comply to stringent safety

standards designed to protect specialty alloys that are used in critical areas of aircraft.

A series of AMS standard tests was conducted to study the effects of

deicers on aircraft metals. Among them is the Total Immersion Corrosion Test,

incoφorated herein by reference, where numerous test panels are suspended in aqueous

solutions of proposed deicers for 24 hours. Test results indicate that potassium succinate

conformed well within the allowable standards for the following aircraft alloys: anodized

AMS 4037 Al alloy, AMS 4041 Al alloy, AMS 4049 Al alloy, AMS 4911 Ti alloy and

AMS 5045 carbon steel.

Example 11

The corrosion inhibitive effects of potassium succinate on dichromate

treated AMS 4376 Mg alloy were compared to that of pure CF7 manufactured by

CRYOTECH of Iowa, potassium acetate (the main constituent of CF7), the DAM claimed

in EP Publication No. 0 077 767 in the form of a potash salt and potassium formate. The

comparison is given in Figure 11. Corrosion of the magnesium alloy was tested in 3 %wt

aqueous deicer solutions for 24 hr, unless otherwise noted. Potassium succinate was

found to be 75% less corrosive than CF7 and 80% less corrosive than potassium acetate, which is the main constituent of CF7. Potassium formate is 13 times more corrosive than

potassium succinate. Further, potassium succinate is 75% less corrosive than the

carboxylate mixture claimed in EP Publication No. 0 077 767.

Example 12

In an effort to formulate a potassium succinate based deicer that exhibited

sufficiently low corrosion to conform to corrosivity standards for dichromate treated

magnesium alloy, the corrosiveness of several compositions that include succinate

derived polycarboxylate salt corrosion inhibiting additives, such as sodium polyaspartate

and polymaleimide sodium salt were investigated.

Mixtures of potassium succinate with sodium polyaspartate and

polymaleimide sodium salt displayed significant improvements in corrosion inhibition

compared to straight potassium succinate. The results are given in Figure 12. While

mixtures of potassium succinate and sodium polycarboxylates can be at least 50% more

effective than straight potassium succinate, the potassium succinate:sodium polyaspartate,

93:7, mixture is 85% more effective. Moreover, the 93:7 mixture of potassium

succinate:sodium polyaspartate conforms to the aircraft metal standard for dichromate

treated AMS 4376 magnesium alloy. In fact, the corrosiveness of this mixture is

approximately 40% less than that allowed by the aircraft metal standard.

Ratios of potassium succinate to succinate derived polycarboxylate salt

corrosion inhibiting additives of between 90:10 and 99:1 are preferred. Exhibit 13

Although accomplishing full conformation on the Total Immersion

Corrosion Test with the 93:7 composition of Example 12 has advantages, it was deemed

further advantageous to find additional formulae containing succinate derived

polycarboxylate salt corrosion inhibiting additives that exhibited superior corrosion

inhibitive properties. Results of some of the successful mixtures are given in Figure 13.

Both mixtures, potassium succinate:magnesium succinate (95:5) and potassium succinate:

magnesium succinate:sodium polyaspartate (95:4:1), were found to be non-corrosive

toward the dichromate treated magnesium alloy. Clearly, the potential for a potassium

succinate based deicer for application in ahports and airbases is enormous. Although,

material cost is always a significant factor in any application, the savings on service and

repair expenditure that can be realized as a result of using a non-corrosive deicer is very

likely to render the use of a potassium succinate based deicer in such high-end

applications economically feasible.

Example 14

Currently, ahplane deicers/anti-icers are liquid formulations based on heavy

alcohols such as propylene glycol. Propylene glycol has good anti-icing properties and

low freezing points in aqueous solutions. A comparison between experimental freezing

points of aqueous propylene glycol and aqueous potassium succinate is provided in Figure

14. The freezing points of potassium succinate and propylene glycol are comparable.

EPO 0 077 767 discloses that the DAM claimed therein has a "pour point and re- liquification point of below -20°C." Clearly, potassium succinate is superior to the DAM

on account of its significantly lower freezing point of below -40°C and superior corrosion

inhibition properties.

Many of the chloride blends consisting of succinate or succinate derived

corrosion inhibitors displayed performance characteristics that exhibited advantageous

properties for use in highway deicing. The tested inhibitors were capable of suppressing

corrosion induced by the chloride salts as much as 50-75 %. This is advantageous

because blends composed of high sodium chloride levels will help in the development of

an affordable product for road deicing applications. In addition, it is unlikely that the

presence of corrosion inhibitors in small quantities will attenuate the ice-penetration and

ice-melting capacities of chloride salts. The anticipated net result will be a family of cost

effective, high-performance deicers that are substantially less corrosive than straight

chloride salts.

Example 15

Deicing chemicals corrode concrete in different ways. Concrete as it is used in

infrastructure may face rebar corrosion in reinforced concrete due to macrocell corrosion,

scaling and spalling or potholing due to concrete surface corrosion. This in turn causes

continuous infrastructure deterioration. Considering just the damage to bridges in the

USA, the U.S. Dept. of Transportation has estimated in 1991 that $90.9 billion will be

needed to repair the damage already incurred to 226,6000 bridges. The enormity of this

type of expense necessitates continuous effort to reduce concrete corrosion. The following experiment evaluates the scaling effect of different salt solutions on concrete

specimens.

To measure the scaling effect of different deicing chemicals on concrete surfaces,

the SHRP H-205.9 test protocol entitled "Test Method for Evaluation of Scaling Effects

of Deicing Chemicals on Concrete Surfaces" from the Handbook of Test Methods for

Evaluating Chemical Deicers, Strategic Highway Research Program, National Research

Council, Report number SHRP-H/WP-90, along with applicable ASTM standards were

followed. Concrete specimens (6 x 12 x 3 inches), two for each salt sample, were

prepared in specially made molds for each sample. Concrete was supplied by a local

concrete mixer. After two stages of 24 hrs (23°C ± 1.7°C and 45 to 55% relative

humidity) and 28 days (14 days at 100% relative humidity according to ASTM C 511-85

and 14 days at 23°C ± 1.7°C and 45 to 55% relative humidity) curing process, the

specimens underwent 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 cycles of freezing/thawing

at a controlled temperature of -17.8°C ± 2.3°C and a relative humidity of about 35%, with

thawing at room temperature. At the end of each five cycles, the salt solutions along with

scaled concrete were collected from the reservoir or the pond of the specimens. The

solutions were vacuum filtered and the residual solids were dried over night and weighed

to determine the quantity of scaled material. Also, at the end of each five cycles, after

removing the scaled material from the specimen, a visual rating of the concrete surface

was given for each specimen according to the guidelines in ASTM C 672-84. The experimental results are presented in Table I and Figure 15. This study shows

that potassium acetate is more corrosive than sodium chloride on the concrete surface,

while there is a minimal scaling for potassium succinate. In addition, visual inspection of

the affected surface of the concrete specimens indicates a no scaling grade for water and

potassium succinate as compared to 3 to 5 for sodium chloride and potassium acetate

which is moderate to severe scaling (coarse aggregate visible over some to entire concrete

surface). Accordingly, potassium succinate makes an excellent deicer for concrete.

One notable accomplishment of the subject application was the discovery of

potassium succinate based deicer formulae that are ideally suited for aiφort and airbase

deicing. Aiφort and airbase deicers need to comply with stringent criteria. These criteria

are set to protect the specialty alloys used in aircrafts. Applicants conducted numerous

experiments using potassium succinate and other corrosion inhibitors to achieve

conformation. Applicants had tremendous success in formulating non-corrosive

potassium succinate based deicers for application in ahports and airbases. Neither CF7

nor DAM that have been formulated for ahport deicing complied with standards for

aircraft metal corrosion.

It will thus be seen that the objects set forth above, among those made

apparent from the preceding description, are efficiently attained and, since certain

changes may be made in carrying out the above method and in the compositions set forth

without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be

inteφreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all

of the generic and specific features of the invention herein described and all statements of

the scope of the invention which, as a matter of language, might be said to fall

therebetween.

Particularly it is to be understood that in said claims, ingredients or

compounds recited in the singular are intended to include compatible mixtures of such

ingredients wherever the sense permits.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A method of deicing aiφort runways or aiφlane surfaces, comprising

applying to an ice covered aiφort runway or aiφlane surface, an ice reducing amount a

deicing composition including an effective amount of a succinate salt, to substantially

reduce the ice on the runway or aiφlane surface.

2. The method of claim 1, wherein the succinate salt comprises potassium

succinate.

3. The method of claim 1, wherein the composition consists essentially of

potassium succinate and at least one polycarboxylate salt corrosion inhibiting additive.

4. The method of claim 1, comprising the step of spreading solid potassium

succinate onto an ahport runway surface.

5. The method of claim 1, comprising the step of deicing an aiφort runway

with a liquid solution containing potassium succinate.

6. The method of claim 1, comprising the step of deicing an aiφlane with a

liquid solution containing potassium succinate.

7. The method of claim 6, wherein an aiφlane is treated with a liquid solution

containing a succinate salt combined with at least one polycarboxylate salt corrosion

inhibiting additive.

8. A method of reducing ice on an ice covered surface of an object comprising

a magnesium based alloy material, comprising applying to the ice on such surface, an ice reducing amount of a deicing composition including an effective amount of a succinate

salt to substantially reduce the ice on the surface.

9. The method of claim 8, wherein the succinate salt comprises potassium

succinate.

10. The method of claim 8, wherein the composition is in a liquid state and

comprises at least one polycarboxylate salt corrosion inhibiting additive in addition to the

succinate salt.

11. The method of claim 9, wherein the solution contains potassium succinate

and at least one polycarboxylate salt corrosion inhibiting additive in a ratio between 90:10

and 99:1.

12. The method of claim 8, wherein the solution contains potassium succinate

and sodium polyaspartate in a ratio of about 97:3.

13. The method of claim 8, wherein the solution contains potassium succinate

and magnesium succinate.

14. The method of claim 8, wherein the solution contains potassium succinate,

magnesium succinate and sodium polyaspartate.

15. A method of removing ice from surfaces, comprising applying to said ice,

an ice removing amount of a deicing composition comprising chloride salts and an

effective amount of a succinate salt to reduce by at least about 20%, the corrosive

properties of the same composition, without the succinate salt, measured by the

corrosiveness to steel of a 3% aqueous solution of the composition.

16. The method of claim 15, wherein the succinate salt component comprises

potassium succinate.

17. The method of claim 16, wherein the succinate salt reduces the

corrosiveness of the deicing composition by at least 50%.

18. A method of removing ice from ice covered surfaces, comprising:

genetically engineering an organism to oveφroduce succinic acid; converting the succinic

acid produced into a succinate salt; and applying a deicing composition comprising the

succinate salt to the surface.

19. The method of claim 18 wherein the surface is a roadway.

20. The method of claim 18, wherein the surface is an ahport runway.

21. The method of claim 18, wherein the surface is of an object comprising a

magnesium alloy.

22. The method of claim 18, wherein the deicing composition comprises

potassium succinate.

23. The method of claim 18, wherein the organism is a bacteria.

24. A deicing composition, comprising chloride salt and about 1 to 10%

succinate salt.

25. The composition of claim 24, wherein the composition comprises 1 to 10%

potassium succinate.

26. The deicing composition of claim 24, wherein the composition comprises 1

to 10% potassium succinate.

27. A deicing composition comprising a succinic acid salt combined with at

least one polycarboxylate salt corrosion inhibiting additive.

28. The deicing composition of claim 27, comprising a succinic acid salt and a

polymaleimide salt.

29. The deicing composition of claim 27, comprising a succinic acid salt and a

polyaspartate salt.

30. The deicing composition of claim 27, wherein the ratio of succinic acid salt

to at least one polycarboxylate salt corrosion inhibiting additive, is about 90:10 to 99:1

31. The deicing composition of claim 27, comprising potassium succinate and

sodium polyaspartate in a ratio of about 97:3.

32. The deicing composition of claim 27, comprising potassium succinate and

magnesium succinate in a ratio of about 95:5.

33. The deicing composition of claim 27, comprising potassium succinate,

magnesium succinate and sodium polyaspartate in a ratio of about 95:4:1.