METHOD FOR REMOVING RUST FROM A SURFACE

Abstract

Described is a method for removing rust from a rusted surface comprising the steps of a) applying to the said surface a first composition comprising a penetrating oil, and b) applying to the said surface a second composition comprising at least one thiol compound, the thiol compound being a thiol substituted carboxylic acid, or a salt or alkyl ester thereof, wherein step b) is carried out prior to, or subsequent, to step a), a kit comprising said first and second compositions, a composition and also to the use of said composition for rust removal.

Claims

1-21. (canceled)

22. A method for removing rust from a rusted surface comprising the steps of: a) applying to the said surface a first composition comprising a penetrating oil, b) applying to the said surface a second composition comprising at least one thiol compound, the thiol compound being a thiol substituted carboxylic acid, or a salt or alkyl ester thereof, wherein step b) is carried out prior to, or subsequent, to step a).

23. The method of claim 22, wherein the thiol compound has a structure according to formula (I): ##STR00003## wherein R=hydrogen or methyl, and X.sup.+ is hydrogen or an alkali metal cation or an alkali earth cation or an ammonium or substituted ammonium cation, preferably X.sup.+ is lithium cation, sodium cation, potassium cation or ammonium cation.

24. The method of claim 22, wherein the thiol compound has a structure according to formula (II): ##STR00004## wherein R.sup.1 is a cyclic, linear or branched alkyl, saturated or unsaturated with 1-22 carbon atoms.

25. The method of claim 23, wherein the thiol compound is thioglycolic acid or sodium thioglycolate.

26. The method of claim 22, wherein the second composition is an aqueous composition, wherein the aqueous composition comprises between 0.1 and 50 wt. % thiol compound with respect to the total weight of the composition.

27. The method of claim 22, wherein at least 1 wt. % thiol compound with respect to the weight of penetrating oil is applied.

28. The method of claim 22, wherein the step a) is carried out before step b).

29. The method of claim 22, wherein the first and/or second composition comprise(s) an emulsifier.

30. The method of claim 29, wherein the first composition comprises between 0.1 and 30 wt. % emulsifier with respect to the total weight of the first composition.

31. The method of claim 29, wherein the second composition comprises between 0.1 and 20 wt. % emulsifier with respect to the total weight of the second composition.

32. The method of claim 29, wherein the emulsifier is selected from the group consisting of polyethylene glycol ethers, primary alcohol ethoxylates and alkyl diglycols and combinations thereof.

33. The method of claim 32, wherein the primary alcohol ethoxylate is selected from the group of primary alcohol ethoxylates having C9-C17 alcohol group and between 3 and 8 moles of ethoxylate.

34. The method of claim 29, wherein the emulsifier has hydrophilic/lipophilic balance (HLB) of between 1 and 18 according to the Griffin index.

35. A kit for performing the method of claim 22, wherein the kit comprises: a) a first holder comprising the first composition as defined in claim 22, b) a second holder comprising the second composition as defined in claim 22.

36. A composition comprising between 0.1 and 50 wt. % of a thiol compound as defined in claim 22, between 0.1 and 20 wt. % of an emulsifier and further comprising between 30 and 99.8 wt. % water with respect to the total weight of the composition, wherein the emulsifier is selected from the group consisting of polyethylene glycol ethers, primary alcohol ethoxylates alkyl diglycols and combinations thereof.

37. The composition of claim 36, wherein the thiol compound is thioglycolic acid or sodium thioglycolate, preferably sodium thioglycolate.

38. The composition of claim 36, wherein the weight percentage of the emulsifier is between 0.5 and 15 wt. % with respect to the total weight of the composition.

39. The composition of claim 36, wherein the weight percentage of the thiol compound is between 1 and 40 wt. % with respect to the total weight of the composition.

40. The composition of claim 36, wherein the emulsifier is selected from the group of primary alcohol ethoxylates having a C9-C17 alcohol group and between 3 and 8 moles of ethoxylate.

41. The composition of claim 36, wherein the emulsifier has hydrophilic/lipophilic balance (HLB) of between 1 and 18 according to the Griffin index.

Description

COMPARATIVE EXAMPLE 1

[0059] The compatibility of different organic acids was tested with commercially available penetrating oil composition (P). In the following example the acids and WD-40 were mixed in a ratio of 1:1 in a test tube and shaken for 5 minutes. 1 minute after shaking the mixtures were visually inspected, wherein + means a stable mixture and means that phase separation was observed.

[0060] Subsequently, the rust removing effect of the tested organic acid-penetrating oil mixtures was studied, after 5 minutes of applying the mixture to an oxidized steel test plate (2 cm5 cm). + means that after 5 minutes rust removal was observed, whereas means that a minimal/no rust removal was observed.

TABLE-US-00002 TABLE 2 Compatibility of organic acids with penetrating oil Mixing ability Acid with WD-40 Rust removal Hydrochloric acid, Sigma Aldrich (Cas No 7647-01-0) (10 wt. %) Citric acid, + Sigma Aldrich (Cas No 77- 92-9) (10 wt. %) Phosphoric acid, Sigma Aldrich (Cas no. 7664-38-2) (10 wt. %) Formic acid, Sigma Aldrich (Cas No 64- 18-6) (10 wt. %) Oxalic acid, Sigma Aldrich (Cas. No 144- 62-7) (10 wt. %) Thioglycolic + + acid, Sigma Aldrich (Cas No 68-11-1) (10 wt. %) Sodium + + thioglycolate 46%, Sigma Aldrich (367- 51-1) (10 wt. %)

[0061] With respect to thioglycolic acid it was observed that this compound slowly gave a purple colour in the presence of rust. For the other acids there was no clear visual indication of a rust removal effect.

COMPARATIVE EXAMPLE 2

[0062] The penetrating oil composition (P) was mixed with sodium thioglycolate and water according to the weight percentages given in the table below. The sodium thioglycolate (powder) appeared to mix well with the penetrating oil. No colour change was observed.

TABLE-US-00003 TABLE 3 Penetrating oil and thioglycolate composition Component Amount/weight percent Penetrating oil (P) 60 Sodium thioglycolate 20 Water 20

[0063] The mixture of sodium thioglycolate in water and penetrating oil, separation of the mixture was observed immediately after mixing.

COMPARATIVE EXAMPLE 3

[0064]

TABLE-US-00004 TABLE 4 Penetrating oil and thioglycolate composition with an emulsifier Component Amount/weight percent Penetrating oil (P) 70 Sodium thioglycolate 10 Water 20 Ethylan 1005 (AkzoNobel) 10

TABLE-US-00005 TABLE 5 Penetrating oil and thioglycolate composition with an emulsifier Component Amount/weight percent Penetrating oil (P) 70 Sodium thioglycolate 10 Water 20 Marlipal O13/30 (SASOL) 10

[0065] Ethylan 1005 and Marlipal O13/30 were used as emulsifiers. Ethylan 1005 is a non-ionic surfactant based on a synthetic primary alcohol (technical data sheet, 18 Aug. 2011, AkzoNobel). Marlipal O13/30 is a surfactant based on alkylpolyethylene glycol ethers (technical data, Sasol Olefins & Surfactants, Isotrideconal Ethoxylates Marlipal 013). In both cases a discolouration was observed, which is an indication for a chemical reaction of the thioglycolic acid with the emulsifier. Furthermore, separation of the mixtures was observed.

EXAMPLE 1

[0066] In a further test system, a mixture of thioglycolic acid, sodium thioglycolate and emulsifiers in water was prepared, in the absence of a penetrating oil composition.

TABLE-US-00006 TABLE 6 Thioglycolate composition with an emulsifier Component Amount Calstar, Sigma 27 Aldrich, Cas. No 7757-93-9, Risella olie X 420. 46 Shell (refined mineral oil, paraffinic) Rokanol, PCC- 5 Exol, (C13 Iso, Alcohol + 12 EO) Sodium 5 thiolglycolate, Thioglycolic acid 5 Butylglycol (Cas 2 No. 111-76-2) Water >100%

[0067] This led to a compatible mixture that did not show any discolouration on standing. The mixture remained homogenous on standing for at least 5 minutes after shaking, which is sufficient time to apply mixture to a surface and for the homogenous mixture to seep into the surface by capillary action. Although this composition is stable, the pH of this solution was about pH 1, which was deemed to pose a health and safety risk for the user. Consequently, a different composition was investigated, as shown in Example 2.

EXAMPLE 2

[0068] A rusted steel plate (2 cm5 cm) was sprayed with 5 mL of a penetrating oil composition (P), after 1 minute 1 mL of a reactive thiol compound was applied, according to the table below:

TABLE-US-00007 TABLE 7 Thioglycolate composition with an emulsifier Component Amount/weight percentage Sodium thioglycolate 20 Marlipal O13/30, SASOL 10 Water 66 Neodol 91/6E (C9-C11 NEODOL 2 alcohol with an average of approximately 6 moles of ethylene oxide per mole of alcohol), Shell Butyldiglycol, Sigma Aldrich, (CAS 2 no. 112-34-5)

[0069] The thioglycolate solution appeared to mix slowly with the penetrating oil present on the test plate, which was apparent due to the slow speed with which the purple colour appeared. The rust was effectively removed from the surface of the test plate.

EXAMPLE 3

[0070] A penetrating oil composition according to comparative example 1 was mixed with Marlipal O13/30 emulsifier (10 wt. %). The penetrating oil composition comprising the emulsifier was added to a steel test plate (2 cm5 cm). Subsequently, the thioglycolate composition according to example 2 was applied to the test plate. A colour change from clear to purple occurred more quickly than when no emulsifier was present in the penetrating oil (i.e. example 2). Addition of an emulsifier to the penetrating oil appears to produce a better mixture of the penetrating oil and thioglycolate solution. Consequently, the thioglycolate solution seeps more quickly into difficult to reach places in order to remove rust and thus to loosen rusted fixings such as screws and bolts.

EXAMPLE 4

[0071] A further thioglycolate solution was prepared according to table 8. The pH of this solution was 6.5

TABLE-US-00008 TABLE 8 Thioglycolate composition Amount/ Component weight percent Sodium 20 thioglycolate Water 76 Neodol 91/6E 2 Butyldiglycol 2

[0072] A rusted steel test plate (2 cm5 cm) was covered with penetrating oil composition (P, 5 mL) and then 0.1 or 1.0 mL of the thioglycolate solutions was applied (examples 5, 6 & 8, table 9). Alternatively, the thioglycolate solution was applied first followed by penetrating oil composition (P, examples 7 and 9).

TABLE-US-00009 TABLE 9 Comparison of rust removal methods according to the invention and controls Result Result after 2 after 15 Example Step a) Step b) minutes minutes Comparative Sodium example 2 Thioglycolate & penetrating oil (P) Comparative Sodium + example 3A/B thioglycolate & penetrating oil (P) [+emulsifier] Comparative Sodium Example 4 thioglycolate solution (46%) Comparative Sodium Example 5 thioglycolate powder (5 g) Comparative Penetrating oil example 6 (P)/5 mL Example 5 Penetrating oil Sodium + ++ (P)/5 mL thioglycolate solution 46%/ 5 mL Example 6 Penetrating oil Solution +++ +++ (P)/5 mL according to example 4/1 mL Example 7 Solution Penetrating oil +++ +++ according to (P)/1 mL example 4/ 5 mL Example 8 Penetrating oil Solution +++ +++ (P)/5 mL according to example 4/ 0.1 mL Example 9 Solution Penetrating oil +++ +++ according to (P)/0.1 mL example 4/ 5 mL : no rust removal observed; +: partial rust removal; ++: intermediate rust removal; +++: complete rust removal

[0073] The results show that applying sodium thioglycolate separately to the penetrating oil composition leads to rust removal on a rusted surface (example 5) compared to treatment with sodium thioglycolate separately or penetrating oil alone. The rust removal can be accelerated when the sodium thioglycolate solution comprises an emulsifier (examples 6-9) relative to a composition comprising thioglycolate and penetrating oil (comparatives examples 2, 3A and 3B).