GB2079310A - Coating of metal and compositions for use in this - Google Patents

Abstract

Lubricant compositions for coating metal surfaces comprise a liquid carrier, lubricant and as corrosion inhibitor a salt of a carboxylic acid with an aliphatic amine. The metal surfaces are preferably metal strip, for instance between manufacture and coiling. The compositions may contain phosphate ions and metal ions.

Description

SPECIFICATION Coating of metal and compositions for use in this It is well known to form a dry lubricant film on a metal surface before subjecting it to deformation, but generally the composition used for this does not give corrosion resistance. Howevervariousproces- ses and compositions are known for forming coatings comprising both a metal phosphate and a lubricant on a metal coating by applying a single composition to the coating. Examples are to be found in British Patent Specifications Nos. 1,371,981, 1,421,386, 1,508,484 and 2035383. Also a process is described by Coupland in Sheet Metal Industries February 1980 pages 180 to 182.

In some instances it is desirable to inhibit corrosion of the metal surface being coated by means additional to the formation of the metal phosphate but the inclusion of conventional corrosion inhibitors will generally have the effect of inhibiting the formation of the metal phosphate coating.

A lubricant coating composition according to the invention for forming lubricant coating on a metal surface, or a concentrate that can be diluted to form a lubricant coating composition, comprises a liquid carrier, lubricant and a corrosion inhibitor which is a salt of a carboxylic acid with an aliphatic amine.

The carboxylic acid is preferably an aliphatic carboxylic acid which preferably contains a long chain, for instance containing 10 to 24 carbon atoms, for instance oleic acid.

The aliphatic amine is preferably a tertiary aliphatic amine in which the aliphatic groups are selected from lower alkyl and lower alkanol groups. It may be a trialkylamine but preferably is a trialkanol amine, wherein the alkyl or alkanol groups preferably contain 1 to 4 carbon atoms.

The preferred amine is triethanol amine and the preferred inhibitor is triethanol amine oleate.

The amount of inhibitor is generally below 1% by weight of the composition, preferably 0.01 to 0.5% by weight.

The lubricant may be any material suitable for forming a dry lubricant film on a metal, and is generally an organic compound containing fatty alkyl, fatty alkenyl, alkaryl ortriterpene radicals having 10 to 36 carbon atoms.

As mentioned, there is a particular problem when the composition is intended both to form a phosphate coating and a lubricant coating and preferably the composition according to the invention is to serve this purpose and includes phosphate ions and polyvalent metal ions.

The composition may be an aqueous emulsion containing cationic emulsifier for emuslification of the lubricant particles. The polyvalent metal is then a coating metal, i.e. a non-alkali metal. Thus the composition may take the form of a phosphate coating solution, or a concentrate suitable for dilution to form a phosphate coating solution, containing phosphate ions, a coating metal and lubricant particles emulsified with a cationic emulsifier. It may include also a scale prevention additive which is a naphthylene sulphonic acid/formaldehyde condensation product or a salt thereof. The lubricant may comprise a mixture of long chain fatty acid and long chain fatty acid ester. Such compositions (but without the inclusion of the corrosion inhibitor of the invention), are described in more detail in British Patent Specifications Nos. 1,421,386 and 2,035,382A.

Reference should be made to these for further details of suitable emulsifiers, lubricants and other components.

The invention is of particular value when the coating composition is applied to steel strip, preferably before it is coiled, and for such purposes the composition preferably has the phosphate, polyvalent metal ions and the lubricant introduced as an acidic reaction product. Compositions of this general type are described in British Patent Specifications Nos.

1,371,981 and 1,508,484 and reference should be made to these for full particulars of such compositions.

Thus the composition preferably comprises a liquid carrier and an acidic reaction product that comprises orthophosphate radicals, polyvalent metal cations and lubricant radicals containing 10 to 36 carbon atoms. The corrosion inhibitor may be included in these compositions merely by admixture with, for instance, the mineral oil or other liquid carrierthat is present in the composition.

The formation of the reaction product may involve the formation of a phosphate ester of the lubricant radicals, which are therefore generally introduced as alcohols. The reaction product is preferably made by heating the polyvalent metal or a compound thereof with orthophosphoric and/or polyphosphoric acid and either simultaneously or subsequently with a compound, generally an alcohol, providing the lubricant radicals. Instead of using a phosphoric acid a phosphate may be used, but the process then usually needs to include an acidification step.

As polyvalent metal there may be used, for exam ple, zinc, manganese, cobalt, nickel, copper, molyb denum, tungsten, aluminium, lead, magnesium, calcium or iron. The metal preferably is not a metal of group IV A of the Periodic Table, for instance as defined in "General and Inorganic Chemistry" third edition by J. R. Partington. The preferred metal is iron, especially when the metal surface is steel.

The polyvalent metal may be supplied in elemental form provided sufficient time for reaction is provided but preferably is introduced in the form of a compound. The compound is preferably metal phosphate although other salts, but preferably not metal halides, may be used. Iron phosphate may be introduced as ferric or, more usually, ferrous phosphate.

The lubricant radicals may be fatty, alkaryl or triterpene radicals. They may be, for example, olefinic radicals, but are preferably alkyl and/or alkaryl radicals. They may be introduced into the reaction mixture by the addition of the corresponding alcohols. The alcohols may be used as pure products or as commercially available impure products.

Suitable fatty alcohols have an average carbon content of 16 to 18 carbon atoms, oleyl cetyl alcohol being preferred. Aliphatic ortriterpene alcohols derived from lanolin are very satisfactory.

The phosphate in the reaction product may be obtained by the use of orthophosphoric acid and/or polyphosphoric acid. Suitable material is commer cially available and preferably contains 76 to 88% by weight P2O5, the remainder being water. It can be prepared by dissolving an excess of solid P2Os in orthophosphoric acid. The resultant product, known as "polyphosphoric acid" or "condensed phosphoric acid" is a mixture of various amounts of orthophosphoric acid in addition to pyro, tri, tetra and higher phosphoric acids. During the preparation of the acidic reaction product some or all of the polyphosphoric acid is converted to orthophosphoric acid.

A preferred reaction product for use in the invention is prepared by heating iron phosphate with orthophosphoric and/or polyphosphoric acid and then heating the product with an alkyl or alkyaryl alcohol having 10 to 36 carbon atoms.

The reaction products are materials that can be put into an organic lubricant carrier to form a single phase system, at least at elevated temperatures. The reaction products are preferably made by reacting the components of the mixture together at elevated temperatures, preferably in the range 60 to 1 50'C for a reaction time of from 30 to 300 minutes. The reaction product is a mixture of various substances and accurate chemical characterisation is difficult.

The product should be acidic and preferably has a pH of less than 3.

The composition that is applied to the metal surface is preferably substantially non-aqueous, generally containing less than 2%, preferably less than 1.5% water, by weight based on the total composition. The amount of water is usually at least 0.1%. In some instances it is particularly useful to use dilute compositions, as described in more detail below, and it is then desirable that the total amount of water should be below 1.5%, preferably less than 1%, with best results generally being obtained with a water content of 0.1 to 0.5%.

The composition may contain for instance from 1 to 60% of the reaction product, by weight based on the total composition. The amount is normally from 1 to 10%, especially when the reaction product is being used for treating steel strip, but higher amounts can be used. In some instances, especially for the treatment of steel strip, it can be desirable to use very dilute compositions containing from 1 to 4 or 4.5% of the reaction product.

The composition may be formed from 0.02 to 0.05% polyvalent metal phosphate, 0.5 to 20% orthophosphoric andíor polyphosphoric acid and 0.5 to 50% lubricant radicals, all percentages being by weight based on the total composition.

The amount of metal phosphate is preferably 0.05 to 0.2% by weight and is preferably iron (generally ferrous) phoshpate. The amount of orthophosphoric and/or polyphosphoric acid is often preferably 0.5 to 5% and the amount of the lubricant radicals is often preferably 0.5 to 5%. These values are especially useful for the dilute compositions mentioned above and for these the preferred amount of polyphosphoric or phosphoric acid is 1.5 to 3.5% and the preferred amount of lubricant is from 1 to 3% and the total amount of ingredients other than the liquid carrier is preferably less than 4%, all by weight based on the total composition.

Preferred compositions according to the invention contain 0.01 to 1%, preferably 0.05 to 0.5%, of the amine salt and are substantially non-aqueous (for instance containing less than 1.5% and preferably less than 1% water, by weight based on the total composition) and are formed from less than 1% metal phosphate, less than 10% orthophosphoric acid and/or polyphosphoric acid, and less than 10% lubricant radicals.

The organic liquid carrier is generally selected so that the coating composition has a viscosity similar to the viscosity of conventional mill oil, or oil type press lubricants for instance 10 to 40, preferably 10 to 30, for instance 19.5, centistokes measured by Kinematic viscometer at 38 C. The carrier is usually a vegetable, animal or, more usually, mineral oil. Suitable oils include brightstock Oil and solvent neutral oils.

The dilution and the amount of the coating composition that is applied to the metal surface is preferably such that the weight of the metal phosphate coating (i.e. the weight of the inorganic components of the final coating) is at least 0.05 glmz and is preferably at least 0.2 g/m2 but is less than 1.5 g/m2, and preferably less than 1 g/m2. In many instances it is desirable to have low coating weights, for instance using the dilute compositions mentioned above.

Thus coating weights of from 0.05 to 0.45 g/m2, preferably 0.2 to 0.4 gjm2 may be suitable.

The invention is of particularvalue in the production of thin coatings of metal phosphate, such as the amounts described above, because of the increased tendency of low amounts of metal phosphate alone to provide adequate corrosion resistance, and corrosion may (in the absence of the inhibitor) occur either during the initial formation of the coating or, in particular, on storage or transport of the coated metal.

The compositions containing the reaction product are of particular value when applied to steel or other metal strip. In traditional methods of strip production oil is applied to the strip before coiling prior to storage and transport. The oil inhibits corrosion during storage and when the strip is to be cold pressed either this oil serves as the lubricant or a lubricant coating is applied.

A preferred method in the invention comprises applying the composition containing the reaction product to the metal strip immediately before coiling the strip and in this method the application of the composition can thus replace the conventional application of mill oil at this stage. Application may be conducted in the same way as mill oil is conventionally applied, for instance by spraying or squeegee It may be applied to just one surface of the strip and then tightly coiled so as to transfer it to the other surface but preferably is applied to both surfaces of the strip and is then tightly coiled. The composition reacts with the metal surface to form a coating that gives corrosion resistance, and thus prevents rusting or other corrosion on storage, and that serves as a lubricant during subsequent pressing operations.

The composition can also be applied prior to pressing, generally after storage and transport, in which event the composition is preferably applied at least 60 minutes before pressing so as to permit adequate reaction between the metal surface and the composition. The composition can be applied to metal surface carrying a film of mill oil, without preliminary cleaning.

Application is generally conducted at ambient temperatures but higher temperatures, e.g. up to 40"C may be desirable especially when it is desired to accelerate the reaction prior to pressing.

The metal that is coated by the composition is generally steel strip, in which event the metal phosphate in the final coating is always iron phosphate but good results are also obtainable when the metal is galvanised steel, in which event the phosphate in the coating will generally be zinc phosphate and iron phosphate.

The invention includes not only the described compositions containing the inhibitor and the described methods of using these compositions but also certain compositions and methods free of inhibitor.

Thus the invention includes a method in which a coating comprising lubricant and 0.05 to 0.45 g/m2 metal phosphate is formed on metal strip by applying to the strip a composition comprising an organic liquid carrier and an acidic reaction product comprising orthophosphate radicals, polyvalent metal cations and lubricant radicals.

The invention also includes a composition suitable for use in this method and which comprises an organic liquid carrier and an acidic reaction product comprising orthophosphate radicals, polyvalent metal cations and lubricant radicals and which is characterised by containing less than 1.5%, preferably less than 1% and most preferably from 0.1 to 0.5% by weight water based on the weight of the total composition, and/or in that the composition contains less than 4.5%, preferably 1 to 4%, by weight of the reaction product based on the weight of the total composition. Preferred amounts of the various ingredients and preferred ingredients in the compositions are all described above, particularly with reference to the description of the dilute compositions mentioned above.

The following are some examples of the invention.

Example 1 0.86 grams ferrous phosphate (Fe3(P04)2.8H20), 24.31 grams of 88% orthophosphoric acid and 16.7 grams oleyl cetyl alcohol are combined by heating at 800C for 90 minutes, and then mixed with 48.76 grams brightstockoil and 1.14grams triethanolamine oleate. The resultant mixture is diluted with sufficient 100 solvent neutral oil to give 1000 grams. During the preparation of the composition the water congent of the components is controlled so that the total amount of water introduced into the composition is between 2.5 and 3.3 grams.

Example 2 0.6 grams of ferrous orthophosphate (Fe3(P04)2.8H20), 17 grams of 88% orthophosphoric acid and 11.7 grams oleyl cetyl alcohol are combined by heating at 100'C for 120 minutes and then mixed with 100 solvent neutral oil and about 1 gram triethanolamine oleate to give 1000 grams. During the preparation of the composition the water content of the components is controlled so that the total amount of water introduced into the composition is between 10 and 15 grams.

Examples 3 and 4 Compositions according to Examples 1 and 2 are prepared by the same method except that the triethanolamine oleate is omitted.

Example 5 Compositions according to any of Examples 1 to 4 are applied by spray or squeegee to both surfaces of steel strip as it comes from the strip mill and the strip is then immediately tightly wound. After transport and storage articles, such as car bodies, can be pressed from the steel strip by conventional press shop methods.

If desired the organic components of the film can then be removed by conventional methods before further processing. The inorganic components can remain on the metal to serve as, for instance, a base for paint or they may also be removed.

Example 6 A concentrate was formed of (all amounts in kg): Triethanolamine oleate 10.0 Stearic acid 34.4 Duomeen TDO 24.0 Polyram S 24.0 Glycerol monostearate 32.0 Phosphoric acid (100%) 68.0 Zinc oxide 5.6 Water q.s. 1,000 "Duomeen" is a trade mark and Duomeen TDO is N - tallow trimethylenediamine dioleate. "Polyram" is a trade mark and Polyram S is a polyaminoethoxylate cationic surfactant.

A 25% by weight solution in water of the above concentrate was formed. The resultant solution contained the lubricant in the form of emulsified particles. 3.2 g/l "Belloid" SFD can be added to the solution. "Belloid" is a trade mark and Belloid SFD is a condensation product as identified in British Patent Specification 2,035,382.

Steel panels could be coated by immersion in this composition.

We have recently described in our specification 2058145 (application 8024466 filed 25th July 1980 claiming priority from 7th August 1979), acidic com positionsforforming a phosphate coating and which comprise phosphate ions, emulsified lubricant water and an emulsifying agent selected from oxazoline waxes and N - tallow polypropyleneamine and mixtures thereof and having a pH at which phosphate coating formation occurs without substantially pickling of the surface, and we describe such compositions containing a corrosion inhibitor which is a salt of a C7-18 carboxylic acid and an aliphatic amine up to C12. We do not claim such compositions herein, and in particular in compositions of the invention in which the lubricant is emulsified we prefer that the emulsifier is not an oxazoline wax or N - tallow polypropyleneamine.

Claims (20)

1. A lubricant coating composition, or a concen trate for formation of a lubricant coating composition, comprising liquid carrier, lubricant and a corro sion inhibitor which is a salt of a carboxylic acid with an aliphatic amine.

2. A composition according to claim 1 in which the acid is an aliphatic carboxylic acid containing a chain of 10 to 24 carbon atoms and the amine is a tertiary aliphatic amine in which the aliphatic groups are selected from lower alkyl and lower alkanol groups.

3. A composition according to claim 2 in which the amine is a trialkanolamine in which each alkanol group contains 1 to 4 carbon atoms.

4. A composition according to claim 3 in which the amine is triethanolamine.

5. A composition according to any preceding claim in which the acid is oleic acid.

6. A composition according to any preceding claim additionally containing phosphate ions and polyvalent metal ions.

7. A composition according to claim 6 in which the phosphate, metal and lubricant are introduced into the composition as an acidic reaction product and the liquid carrier comprises a substantially non-aqueous liquid.

8. A composition according to claim 7 in which the reaction product is made by heating polyvalent metal or a compound thereof with orthophosphoric or polyphosphoric acid and an alcohol that includes fatty CtO~3X; radicals.

9. A composition according to claim 7 or claim 8 in which the liquid carrier is a mineral oil.

10. A composition according to claim 9 in which the liquid carrier is brightstock oil or solvent neutral oil.

11. A composition according to any of claims 7 to 10 containing less than 2% water and containing from 1 to 60% by weight of the reaction product and which has been formed from 0.02 to 0.5% polyvalent metal phosphate, 0.5 to 20% orthophosphoric and/or polyphosphoric acid and 0.5 to 50% lubricant radicals all percentages being by weight based on the total composition.

12. A composition according to claim 11 in which the water content is from 0.1 to 1.5% and the composition contains less than 4.5% by weight of the reaction product and is formed from 0.02 to 0.5% polyvalent metal phosphate, 0.5 to 5% orthophosphoric and/or polyphosphoric acid and 0.5 to 5% lubricant radicals, all percentages being by weight based on the total composition.

13. A composition according to claim 6 in the form of an aqueous emulsion containing cationic emulsifier for emulsification of the lubricant particles.

14. A composition according to claim 7 in which the lubricant comprises a mixture of long chain fatty acid and long chain fatty acid ester and the metal is a coating metal.

15. A composition according to any of claims 1 to 6, 13 or 14 in which, if the lubricant is present as an aqueous emulsion including an emulsifier, the emulsifier is not an oxazoline wax or N - tallow polypropyleneamine.

16. A composition according to claim 1 substantially as herein described with reference to any of the examples.

17. A method in which a composition according to any of claims 7 to 12 is applied to metal strip.

18. A method according to claim 16 in which the composition is applied to metal strip between its formation and before coiling the strip.

19. A method in which a coating containing lubricant and 0.05 and 0.45 g/m2 metal phosphate is formed on metal strip by applying to the strip a composition comprising an organic liquid carrier and an acidic reaction product comprising orthophosphate radicals, polyvalent metal cations and lubricant radicals.

20. A composition comprising an organic liquid carrier and an acidic reaction product comprising orthophosphate radicals, polyvalent metal cations and lubricant radicals and which is characterised in that it contains less than 1.5% by weight water and/or that it contains less than 4.5 /0 by weight of the reaction product, the percentages being by weight based on the total composition.