WO2005023957A1

WO2005023957A1 - A novel deicing composition and use thereof

Info

Publication number: WO2005023957A1
Application number: PCT/SE2004/001280
Authority: WO
Inventors: Jukka Hietala; Mircea Manea
Original assignee: Perstorp Specialty Chemicals Ab
Priority date: 2003-09-08
Filing date: 2004-09-07
Publication date: 2005-03-17
Also published as: SE0302396L; SE0302396D0; SE526350C2

Abstract

A novel deicing composition having improved corrosion inhibition and comprising 89-99.5% by weight of an alkali metal formate, 0.25-6% by weight of an alkali metal silicate and 0.05-5% by weight of an alkali metal alkyl sulphate is disclosed.

Description

A NOVEL DEICING COMPOSITION AND USE THEREOF

The present invention relates to a deicing composition comprising one or more alkali metal formates as main constituent. In a further aspect, the invention relates the use of said composition for melting and/or thawing, that is deicing and/or anti-icing of, snow and/or ice on primarily traffic areas, such streets, roads and airfield runways.

Removal (deicing) and prevention (anti-icing) of frost, ice or snow accixπrulation on for air traffic critical areas, such airfields, are essential for a safe air traffic. Snow and ice on streets, roads, cycleways, footpaths, bridges, backyards, parking areas, sportsgrounds and other trafficked areas lead to a substantial impairment in personal, traffic and transport safety etc. It has therefore long been known to apply to said areas a composition for melting and/or thawing snow and/or ice. The materials from which said areas made, such as concrete and metals, must not be damaged or otherwise destroyed by the deicing composition. It is also essential to rule out corrosive actions on metals, especially light metals used in for instance aircrafts. Furthermore, a deicing composition may enter the wastewater and biodegradability is thus a further requirement. It is also essential that very rapid thawing is achieved.

hi order to remove snow and ice both solid and liquid deicing compositions are used. Solids form brine which penetrates first to the ground and moves then outward melting and undercutting the snow and ice. Known and commonly used deicers in said areas include sodium formate, potassium formate, sodium acetate, potassium acetate, magnesium acetate, urea, ethylene glycol and propylene glycol. Urea is not recommended anymore because it degrades to ammonia, which has undesired environmental effects, and because urea looses its ability to melt and/or thaw snow and ice at temperatures below — 7°C. Sodium formate works efficiently at low temperatures and is regarded to have low or insignificant environmental side effects, but is corrosive and corrosion inhibitors must be added before it can be used as deicer.

A critical test for air traffic related deicers is the immersion corrosion test described in ASTM F 483 and AMS 143 IB, stating that panels of dichromated magnesium alloy AZ31B-H26 must tolerate 5% by weight as well as 15% by weight of an aqueous deicer solutions at 38°C with a weight change of said panels being less than 0.2 mg/cm² during 24 hours.

Many attempts have been made to solve the problem with corrosion by the use of inhibitors. EP 0 375 214 discloses a liquid deicer consisting of 45-60% by weight of an alkali metal acetate and/or alkali metal formate, 0.1-0.4% by weight of an alkali metal phosphate and 0.2-0.6% by weight of an alkali metal nitrite. The inhibitor effect of alkali metal phosphate and alkali metal nitrite leaves much to be desired, especially with regard to magnesium. A further disadvantage is the nitrite content. DE 40 34 217 teaches a liquid or solid deicing composition based on water soluble alkali metal salts of formic and/or acetic acid with a corrosion inhibitor system consisting of water soluble polycarboxylic acids and water soluble alkali silicates and/or carbonates. The deicing composition is said to attack neither constructions of concrete, bitumen or stone, nor metallic materials such as iron, copper, aluminium or zinc. US 4,803,007 describes a deicing composition based on sodium chloride and wherein a mixture of a divalent metal salt and an alkali metal polyphosphate is employed as corrosion inhibitor. Divalent metals mentioned include calcium, magnesium and barium with borates, metasilicates and sulphates as counter ions. This inhibitor combination acts in particular to counter corrosion to ferrous metals, but less so with respect to the corrosion of light metals such as magnesium. US 6,059,989 teaches a deicing composition consisting essentially of 87-99.45% by weight of an alkali metal acetate and/or formate, 0.5-10% by weight of an alkali metal silicate and 0.05-3% by weight of an alkali metal phosphate as corrosion inhibitor. The composition is claimed to ensure short thaw time and corrosion protection, especially with regard to magnesium.

It is, furthermore, known to use alkali metal metasilicates, such as sodium metasilicate

(Na₂Siθ₃), to increase the pH in areas wherein a test metal corrodes only slowly and to give a protective silicate layer. Sodium metasilicate is a well known inhibitor frequently disclosed in the literature. Alkali metal metasilicates do, however, not give enough protection towards corrosion of magnesium in formate solutions, why additional inhibitor(s), such the frequently used alkali metal phosphates and carboxylates, must be added.

The present invention quite surprisingly disclose a novel deicing composition exhibiting improved corrosion inhibition. The deicing composition comprises an alkali metal formate, an alkali metal silicate and an alkali metal alkyl sulphate. The amounts of the three components, with or without additional components, can be varied within wide limits. The preferred amount of said three components is, however, 89-99.5%, such as 94-99.4%, by weight of said alkali metal formate, 0.25-6%, such as 1-3%, by weight of said alkali metal silicate and 0.05-5%, such as 0.5-3%, by weight of said alkali metal alkyl sulphate. Said weight percentages are calculated on dry substances.

Said deicing composition is prepared by mixing the liquid or solid components and can thus be used in solid form, for instance as a powder or granules, or as an aqueous solution comprising for instance 5-60%, such as 10-50%, 15-45% or 20-40%, by weight of said deicing composition.

Said alkali metal formate is in especially preferred embodiments sodium formate and said alkali metal silicate is preferably a metasilicate, such as sodium metasilicate. Preferred embodiments of said alkali metal alkyl sulphate include alkali metal Cg-Cjs alkyl sulphates. The most preferred alkali metal alkyl sulphate is sodium lauryl sulphate (sodium dodecyl sulphate).

In a further aspect, the present invention refers to the use of a deicing composition as disclosed above in deicing and anti-icing of for instance airfields, streets, roads, cycleways, footpaths, bridges, backyards, parking areas and sportsgrounds and other trafficked areas in need of deicing and/or anti-icing.

The novel deicing composition is particularly suitable for and air traffic areas, such as runways (take off and landing), parking areas, bus routes and the like and is preferably employed in solid form, such as powders, granules and the like. The deicing composition according to the present invention exhibits improved corrosion inhibition over for instance carboxylates and phosphates as disclosed in the prior art.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilise the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever. In the following Examples 1 and 5-7 refer to embodiments of the deicmg composition of the present invention and Examples 2-4 and 8-9 to comparative deicing compositions outside the scope of the present invention. The deicing compositions of Examples 1-8 were prepared by mixing the components and stated percentages are percentages by weight. Examples 9 and 10 illustrate said the corrosion inhibition obtained by the deicing compositions of Examples 1-8. The result is presented in Tables 1 and 2.

Example 1

Sodium formate, % 93.3 Sodium metasilicate, % 2.0 Sodium lauryl sulphate, % 4.7 (16 mmole/dm³)

Example 2 (Comparative)

Sodium formate, % 95.2 Sodium metasilicate, % 2.0 Sodium octoate, % 2.7 (16 mmole/dm³) Example 3 (Comparative)

Sodium formate, % 94.4 Sodium metasilicate, % 2.0 Sodium dodecanate, % 3.6 (16 mmole/dm³)

Example 4 (Comparative)

Sodium formate, % 96.0 Sodium metasilicate, % 2.0 Potassium phosphate, % 2.0

Example 5

Sodium formate, % 97.5 Sodium metasilicate, % 2.0

Sodium lauryl sulphate, % 0.5

Example 6

Sodium formate, % 97.0

Sodium metasilicate, % 2.0

Sodium lauryl sulphate, % 1.0

Example 7

Sodium formate, % 96.5

Sodium metasilicate, % 2.5

Sodium lauryl sulphate, % 1.0

Example 8 (Comparative)

Sodium formate, % 97.2

Sodium metasilicate, % 2.5

Potassium phosphate, % 0.3 Example 9 (Comparative)

Sodium formate, % 96.2 Sodium metasilicate, % 2.5 Sodium lauryl sulphate, % 1.0 Potassium phosphate 0.3

Example 10

Immersion corrosion tests with 10% by weight solutions in water of the deicing compositions of Example 1 and comparative Examples 2-4 were performed according to ASTM F 483 and AMS 143 IB (as disclosed above). Panels of dichromated magnesium alloy was immersed at a solution temperature of 38°C during 24 hours. The weight change of the dichromated magnesium alloy panels was recorded after said time.

The test results are given in Table 1 below and show that deicing compositions according to the present invention exhibit improved corrosion inhibition.

Example 11

Immersion corrosion tests with 15% by weight solutions in water of the deicing compositions of Examples 5-7 and comparative Examples 8 and 9 were performed according to ASTM F 483 and AMS 143 IB (as disclosed above). The panels of dichromated magnesium were, however, immersed at a solution temperature of 38°C during 66, 168 and 240 hours. The weight change of the dichromated magnesium alloy panels was recorded after said time.

The test results are given in Table 2 below and show that deicing compositions according to the present invention exhibit improved corrosion inhibition.

Table 1

Table 2

Claims

1. A deicing composition characterised in, that it comprises 89-99.5% by weight of an alkali metal formate, 0.25-6% by weight of an alkali metal silicate and 0.05-5% by weight of an alkali metal alkyl sulphate, said weight percentages being calculated on dry substances.

2. A deicmg composition according to Claim 1 characterised in, that it comprises 94-99.5%) by weight of an alkali metal formate, 1-3% by weight of an alkali metal silicate and 0.5-3%) by weight of an alkali metal alkyl sulphate, said weight percentages being calculated on dry substances.

3. A deicing composition according to Claim 1 or 2 characterised in, that said alkali metal formate is sodium formate.

4. A deicing composition according to any of the Claims 1-3 characterised in, that said alkali metal silicate is a metasilicate.

5. A deicing composition according to any of the Claims 1-4 characterised in, that said alkali metal silicate is sodium metasilicate.

6. A deicing composition according to any of the Claims 1-5 characterised in, that said alkali metal alkyl sulphate is an alkali metal Cg-Cis alkyl sulphate.

7. A deicing composition according to any of the Claims 1-6 characterised in, that said alkali metal alkyl sulphate is sodium lauryl sulphate.

8. A deicing composition according to any of the Claims 1-7 characterised in, that said composition is a solid powder or solid granules.

9. A deicing composition according to any of the Claims 1-7 c h a r a c t e r i s e d in, that said composition is an aqueous solution.

10. A deicing composition according to Claim 9 characteris ed in, that said aqueous solution comprises 5-60%, such as 20-40%, by weight of said three components.

11. Use of a deicing composition according to any of the Claims 1-10, in areas in need of deicing and/or anti-icing.

12. Use of a deicing composition according to any of the Claims 1-10, in deicing and anti-icing of airfields, airfield runways, streets, roads, cycleways, footpaths, bridges, backyards, parking areas and sportsgrounds.