DE1546161A1 - Process for cleaning metal objects - Google Patents

Description

1BERLIN33 ualic Biieruvc 8MÜNCHEN27

Augu «te-Viktori« -Strt8e 66 Df.- Ing. HANS RUSCH KC Pieraenauer Strasse 2

Pat..A "w.pr. *" *. Dipl.-Ing. HE! NZ AGULAR ^Pmt - ^Anw " ^tA Ä

ρΓΙΖ! PATENT Attorneys ^ j

Postal check account: Postal check account: Berlin West 7494 4 / - / Tq Munich «277 Bank account: MI QOO Bank account for trade and industry Dresdner Bank DepositonkMs.32 Dr .U / SC hl · Munich

Telegram address: ■ Telegram address: Quadrature Berlin Quadrature Munich

Minnesota Mining and Manufacturing Company, Saint Paul, Minnesota 55 119, V.St.A.

Process for cleaning metal objects

The invention relates, in particular, to the cleaning of metal objects prior to the application of a coating material prior to the application of a metal by mechanical Plate. .

In recent years, mechanical plating has grown displaced electroplating in many fields, in particular With relatively small metal objects · In mechanical plating, the objects are first cleaned, etched and removed to remove metal oxide, oil and dirt then together with finely divided metal powder, a promoterch emi kai ie and, in general, impact media in a plating drum given »when the plating drum rotated or is moved in another way, the e.M et allpulvert are quickly

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Chen pressed flat against the surface of the objects and form a cohesive coating. Although mechanical plating is convenient and requires little work space, the facilities required to clean the surfaces prior to plating are inappropriately large occupied part of the space available in the establishments

For many years it has been customary to start metal surfaces with the help of a series of steps to clean the procedure carried out Degreasing of impurities, which is done either with the help of trichlorethylene vapor or by immersion in a container, which contains an alkali solution * The defatted objects are then removed, rinsed in a second container, removed, derusted or freed from their oxide coating Treatment is pickled with an acid, which is done by immersion in a third container, removed and rinsed again, which is often done in a fourth container. The containers occupy a considerable tree, which inevitably adds to the cost of the process. With this species and manner of cleaning is also a constant monitoring the strength and contamination of the treatment baths required, and the open containers pose a serious danger to the worker "! if continued to bend high carbon steels or inappropriately degreased metal objects

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will »n; sg. _t: minter, the inorganic acids used for pickling leave a carbon dirt on: the metal surface, -.f ^ dtpcfci.rdie. . He Contro l zi .- a uniform coating with the ** Ibeizugsmat eri-al, outer sts CHWI he i; g, * ti ei t.er ^ hi η- g elangt durjsjl | as _Jiiit: .the? -> Pickling acids carried out in the metal: metal lattice, which makes the metal more brittle. (this phenomenon is referred to as "hydrogen embrittlement"), which is often the case. Rupture of the cleaned and then. electroplated metal object leads. /. ■,. -;

, ..; _d according to the invention .. will be for the first time a. uniform,. einstufigesι zur..vollständigenBeinigung .A, ^ and _{Oxydschichtentfernung;} Degreasing, yon; ζω. Plating.metal articles proposed · For, the entire process,. a single: container can be used; whereby great economic efficiency is achieved both in terms of the relaxation time and in terms of the required work station. The method according to the invention is convenient and eliminates the need for constant and careful monitoring of several treatment baths and the transfer of the Metal objects from one bath to the other. Is simple and cheap and delivers consistent and predictable results _? - According to the invention, the e become the unifying i! Metal objects in ■■ a: Containers (which can be the same drum _: which is used for mechanical plating) -given ,, and .es. is a small yerhältnismäßig _a Meiige einer..wäßrigen .Heinigungslösung and yorzugsweise, you Impact, or impact media ^ u (. EEnter "The. counter,

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stands and the solution are moved or «stirred until the objects are cleaned, after which the cleaning solution is drained is finished, with the cleaned, degreased, freed from the oxide layer, de-soiled and etched objects ready left for plating. By discarding the used Cleaning solution - which would not be economically viable with an immersion cleaning process - contamination is avoided and facilitates quality control «For cleaning metal objects using the method according to the invention a new and useful metal cleaning compound has been developed, which consists of a combination of components that facilitate the implementation of the procedure. This combination of substances causes the different ones quickly and at the same time and previously separately performed operations of degreasing, oxide layer removal, desmutting and des Etching, while the problem of hydrogen embrittlement is practically eliminated «, the cleaning compound consists of one water-soluble mixture of an acid suitable for removing metal oxides, an inhibitor that prevents hydrogen embrittlement capable of inhibiting, and a surface-active agent that fulfills the combined functions of metal wetting, oxide layer removal, dirt removal and oil emulsification able »

When in the cleaning solution for the oxide layer removal The acid used can be a mineral acid or be an organic acid. Mineral acids have the advantage

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that they are relatively cheap, while organic acids Allow easier regulation of the process and at tree temperature are less corrosive. For the removal of oxide layers and for the itching of 10,000 g of typical metal objects an amount of acid required that contains 1 to 5 grams of "available" hydrogen ions able to deliver · Both monobasic and polybasic acids can be used, but is used for the purposes according to the invention a fasserstoffion as "available" considered if the for the dissociation of this tifasserstoffions applicable ionization constant is at least 10. To reduce hydrogen embrittlement to a minimum, the incorporation of an inhibitor which is able to inhibit hydrogen embrittlement is also preferred. Whether an InM ^ bitor is or is not effective in the context of the particular acid used can be described empirically using known methods, such as in the example below is explained.

In general, that of the surface-active Agents can best achieve the required range of properties by mixing different surface-active agents with one another, which are similar in their ionic nature, but have different surface-active properties. A well-known one A method of classifying surfactants is to determine the ratio between their hydrophilic properties and their lipophilic properties, according to the English Name "hydrophilelipophile balance" under the abbreviation

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"HLB value" known. This is a tasting process this in detail by William C. Griffin, see e.g. Journal of the Society of Cosmetic Chemists, Volume I, 1949, Pages 311-326, and Volume V, 1954, pages 249-256. A more theoretical procedure exists in determining the value φ ^, the ratio of the oil volume to the water volume at the turning point between oil-in-water and Water-in-oil emulsions, and with the help of "well-known

Th graphical determination of the HLB value carried outj cf. J.T.Davies and E.K '«Bideal," Interfacial Phenomena ", 1961, Academic Press, New York and London, pages 378-383.

Surfactants are compounds which have a hydrophilic part and a hydrophobic or lipophilic part so that, in other words, the HLB value is based on the Relation between the hydrophilic and the lipophilic groups in the molecule. Surfactants in which the lipophilic groups predominate, are oil-soluble and therefore extremely

fe effective for wetting of surfaces which are contaminated with organic substances, such as B _{# 0}} with oils such surfactants have an HLB value of 5 or below. Surfactants containing approximately equal numbers of hydrophilic and lipophilic groups have an HLB rating within the approximate range of 12-17 and act as detergents when their molecular weight is relatively low and as emulsifiers when their molecular weight is relatively high. Surfactants in which the hydrophilic

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Groups predominate, have an HLB value of over 17 and are effective as a dispersant for carbonaceous and other such substances.

According to a preferred embodiment of the invention, a mixture of surface-active agents is used. One of these surfactants - a heating agent that dissolves oil and dirt and assists the acid in evenly touching the metal oxide layer - has an HLB value within the range of 1 to 5. Another surfactant - a cleaning agent that works when suspended Soil and oxide layer constituents helps - has an HLB value within the range of $ 12-17 and a third surfactant - an emulsifier that emulsifies residual oils - also has an HLB value within the range of 12-17 "Desirably there is also a fourth surfactant - a dispersant that prevents agglomeration and re-separation of the particles and has an HLB value above 17 "

As explained in the previous paragraph, the invention Legging mass have an emulsifying power. The objects to be cleaned are often delivered in a very oily condition. 10,000 g metal objects can ζ, Β * Contain 150 g or more of oil. A convenient way of predicting the emulsifying power of a surfactant consists in the determination of the value ^ (and from it the HLB- ¥ ¥ ertes) with the help of an Eraulgiermaschine of the kind

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on page 378 u, f "of the above-mentioned book by Davies and Rideal". In this machine, ligroin and water are pumped in through flow meters from separate reservoirs at controlled speeds and introduced between two shear plates made of polymethyl methacrylate. The flow of the emulsion hits a window Polymethyl methacrylate, and a continuous white film appears if the oil phase is continuous, or white drops appear if the water phase is continuous.A precise method of determining the turning point is to measure the conductivity of the emulsion, which corresponds to the The transition from the water-in-oil system to the oil-in-water system decreases sharply and, conversely, the transition from the oil-in-water system to the water-in-oil system rises steeply * The flow rates are set so that the oil / water -Ratio at the phase reversal point, d * h * the value §s _{t is} obtained *

To further explain the invention, a currently preferred cleaning composition and the method are described below described for their production · All parts are - unless otherwise stated - parts by weight ·

example Hydrogen fragrance inhibitor

32.0 parts of a water-soluble polyoxyethylene glycol are added to 50.2 parts of deionized water. The mixture is heated to 5O ⁰ C and kept at this temperature,

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until all of the polyoxyethylene glycol has dissolved and a uniform solution has formed. The temperature is then reduced to 25 ^° C., whereupon 4.8 parts of concentrated hydrochloric acid, 6.5 parts of o-toluidine and 6.5 parts of 37 # formaldehyde are added and the reaction vessel is closed. When the exothermic reaction has ended, is the feed shortly heated to 5Q ⁰ C, cooled to 30 ⁰ C and withdrawn from the container. This mass is subsequently referred to as "mass A" »

Production of the metal cleaning compound

The following ingredients are placed in a stainless steel kettle:
70% grlycolic acid 84.4

Heat and acid resistant, non-toxic, nonionic surfactants with a hydrophobic Polyoxypropylene core and two hydrophilic. Polyoxyethylene chains as commercially available from the iiYyandotte Chemical Company under the trade name "Pl uronic" are available - Liquid Carbon Dirt Removal Mi ^

tel with an average molecular ^

weight of about 2900, of which the polyoxy * '

propylene core 1750, and a SMa-

Value of about 15; in trade as "Plurossic

L-64 "available / 1.8

Liquid final and anti-foaming agent with

an average molecular weight

of 3500, of which the polyoxyprop linkers

is about 325Ö, and a! 'HtI value of

about 1 j in the trade as "Pluronic / L-IOI".

available 7 1.8

, / s

Agitation is commenced; and the following normally solid surfactants become molten

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Form added:

Cleansing agents having an average molecular weight of about 450O _{1 of} which the core is about 2250 and an HLB of about 16; commercially available as "Pluronic P-85" 1.8

Emulsifiers having an average molecular weight of about 5500. of which the Core is about 3250, and has an HLB of about 13; commercially as "Pluronic P-104 "available 1.8

Mixing continues until the solution is uniform. At this point 4.4 parts of "Compound A" are slowly added. Mixing is continued until the solution is completely uniform. The final mass has a specific Weight from 1.23 to

The cleaning compound described is extremely useful for a wide variety of metal cleaning operations, although Metal objects can vary in terms of their surface area and the amount of oiyd layer on them, and although such articles are often not completely contaminated with oil, the above-described cleaning compound is among the most difficult for cleaning operations Conditions that are conceivable, suitable.

With the help of the novel method of the invention can simultaneous mechanical and chemical cleaning of metal objects that are subsequently to be coated. The objects are placed in an aqueous oxide layer removal and degreasing liquid, which then vigorously stirred or moved while the objects to

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Loosening of the oxide layer and the oil can be cleaned mechanically. laughter completing the leg will be the items rinsed and then coated as desired. The cleaning and rinsing process is conveniently carried out in an inclined manner Rotary drum carried out with an open end, the pneumatic tire of the objects entering during the rotation of the drum on top of each other and on the walls of the drum to loosen the ozyd layer, the oil and the dirt, with which the metal object is contaminated. The mechanical cleaning can be made more effective if the loading is small Particles or impact media incorporated.

In a typical cleaning operation, 170 liters of metal items to be cleaned are placed in an inclined octagonal 760 liter rotary drum. Be in the drum then 3 liters of the cleaning solution from the above example, 115 liters of water and 170 liters of impact media (such as ζ · Β · a mixture

/ en

of glass beads, of which / 90 ^ have an average diameter of 0.30 to 0.56 mm and 10 $ a diameter of 0.15 to 0.18 mm). Live steam is then introduced in order to bring the charge to almost 100 ^° C. and the drum is set in motion about 45 liters per minute is supplied. The excess liquid is then decanted off, and there will be - if the mechanical plating in the same

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Drum is to be carried out - a common anchoring solution (such as a copper plating solution) and a feed for mechanical plating introduced sequentially «When the cleaned items painted, electroplated or are to be coated in another way, they are screened off by the impact media and transported to the next treatment station! ert.

During a test (see Society of Automotive Engineering Test Procedure SAE 1065-1080) to determine the hydrogen embrittlement caused by cleaning is a Standard spring wire hose clamp made of steel with a high carbon content, which has a Bockwell G hardness of at least 53, cleaned, plated and, after a given period of time, pulled apart with a standard instrument and pulled over a rod that has a slightly larger diameter than the inner diameter of the clamp. if Hydrogen embrittlement occurred at the hose clamp the clamp will break either immediately or within 24 hours. In general, the probability is one The shorter the time before the test, the greater the break. A total of 150 No. 15 hose clamps were made as described above cleaned, provided with a copper anchoring coating and immediately mechanically plated with zinc. 4 hours after After plating, 50 of the clamps were placed on a test stick with a 2.421 cm in diameter and none of the clamps broke within 24 hours. 24 hours after plating

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the other 10Ü terminals were attached to the test rod; again, no fracture of any occurred within 24 hours the terminals on »

Of course, the above example is illustrative only and numerous changes can be made will. For example, numerous other acids - or mixtures of acids - can be used. Mineral acids, such as sulfur and phosphoric acid, are strong and relatively cheap, and offer obvious economic advantages Mineral acids in concentrated form attack even permanent surfactants, it often is it is preferable to add the acid and the other ingredients separately at the time of cleaning furthermore, when the stronger inorganic acids are used, a rapid dissolution of the metal occurs, and often - especially with Steel objects with a high carbon content or heat-tempered Steel objects - carbon dirt remains the surface. These phenomena can be eliminated by adding a small amount of one or more soluble salts, such as the sulphates of tin, lead, cadmium, mercury, etc. are reduced are, iis under these conditions it is furthermore desirable to ensure that in the mixture of the surface-active Means a dispersant for carbon dirt, d, h « a surface active one. Means with. high HLB value, is included » As is known, phosphoric acid offers particular advantages if the surface to be cleaned is then coated with a coat of paint

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should be provided. Similarly, it is convenient to use the acidic salts of mineral acids (such as sodium bisulfate or monobasic sodium phosphate) or salts that hydrolyze to form "available" hydrogen ions (such as aluminum chloride or ammonium sulfate).

Many other organic acids, both monobasic and more basic, can be used. E.g. tartaric acid, citric acid, diglycolic acid, chlorosulfonic acid, Formic acid, acetic acid and mono-, di- or trichloroacetic acid to be used. When calculating the available hydrogen ions that an acid can deliver, only those are Acid residues with a dissociation constant of at least 10 are considered effective. Acids that may be considered too are viewed poorly, obtain higher effectiveness at the preferred elevated cleaning temperature.

Grlycolic acid has the advantage of being a complexing agent and therefore competes with the oxygen for the metal ions in the oxide coating. If that continues for The cleaning water used contains ions that enhance the cleaning effect interfere, the glycolic acid helps to bind these ions through complex formation. If using an acid, the. This property does not have the addition of a ^ complexing agent if desired, other acid-resistant complexing agents can be added. So can the sodium salt of diethylenetriaminepentaacetic acid, commercially available from Dow Chemical Company under the trade designation "Versenex 80"

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available, can be used.

The surface-active agents of the above example can be used in an excellent manner, since their resistance, their chemical similarity and their physical properties have been determined. The mixture of surfactants However, the agent in the cleaning solution described can contain all acid-resistant substances with a suitable HLB value, which have the following ionic nature: all anionic; a mixture of anionic and nonionic; all non-ionic, a mixture of non-ionic and canonical; or all cationic. The cationically modified surface-active amides derived from oils such as ethylene oxide modified coconut oil amide such as es is commercially available under the name "Ethomeen e / 25", or hydrogenated tallow amide modified with ethylene oxide, as is commercially available under the name "Ethomid HT 25" (both products are marketed by Armor Industrial Chemicals Go »), are adsorbed on metal surfaces, reduce the need for use of Wetting agents with a low HLB value and otherwise help difficult cleaning of metal objects that have a thin, firmly adsorbed film, such as a sulfonated oil, exhibit.

line number of substances has empirically proven to be suitable for inhibiting hydrogen embrittlement. The "mass A" described in connection with the above example

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contains a combination of substances that are individually effective in this regard. Both the polyoxyethylene glycol as Also the o-toluidine are capable of hydrogen embrittlement to reduce or suppress even at high temperatures, In "mass A" some of these substances are reacted with one another been, being an adduct of o-taluidine and formaldehyde which is stable and has an excellent inhibiting effect. Practically, however, there can be a great variety of commercially available inhibitors, such as with ethylene

^w oxide modified tree resin amine - as it is commercially available from the

Hercules Powder Oo "available under the name" Polyrad 1110A " is -, 2-hexyne-3 ~ Q1, substituted thioureas, as well as most amines or proteins, with at least some Degree of success can be used. Inhibitors, however, are at least to some extent selective, and a given Inhibitor may be more effective with one acid than with another.

- patent claims -

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Claims (14)

Patent claims 1. A method for cleaning metal objects for the subsequent coating, characterized in that (1) the metal objects to be cleaned and an aqueous degreasing and oxide layer removal solution are placed in a container, (2) the solution is moved vigorously, preferably by rotating the container around its Axis, while the objects are mechanically cleaned, preferably with the aid of impact media, and (3) the objects are rinsed _e 2. The method according to claim 1, characterized in that that the degreasing and oxide layer removal solution is water, a strong acid, an inhibitor to inhibit hydrogen embrittlement and contains a surface-active compound that performs the combined functions of metal wetting, oxide layer removal, Able to perform oil emulsification and dirt dispersion * 3 »Method according to claim 2, characterized in that that the surface-active composition is a mixture of surface-active substances whose HIB-tate within a wide range Range. 4. Method according to claims 1-3, characterized in that the solution is heated, preferably by introducing γ on live steam. 909829/1294 5. The method according to claim 2, 3 or 4, characterized in that the strong acid is glycolic acid » 6 _# A method according to claim 2, 3, 4 or 5, characterized in that the strong acid 1 is capable of providing per 10 000 parts metal objects to 5 parts available hydrogen ions and that the surfactant used for emulsifying 150 parts of mineral spirits per 10 000 parts Metal objects is capable. 7. The method according to claim 3, 4, 5 or 6, characterized in that that each of the surfactants has a hydrophobic polyocypropylene core and grafted onto it having hydrophilic polyoxyethylene units, and that one of the surfactants one wetting agent with an HLB value within the range of 1 to 5 »a second a cleaning agent with an HLB value within the range of 12-17, a third an emulsifier with an HLMert within the Range from 12-17 and a fourth is a dispersant with an HLIMert above 17. 8 _# Water-soluble composition suitable for use in the method of claim 1, characterized in that it contains a surface-active agent with coordinated properties, an acid suitable for removing metal oxides and an inhibitor for inhibiting hydrogen embrittlement, the surface-active agent having the combined functions of metal - 909829/1294 SAD ORIGINAL _1t . _{/ c1c1} M 1668 wetting, oxide layer removal, oil emulsification and dirt dispersion able to exercise. 9 # mass according to claim 8, characterized in that the surfactant of a variety of surfactants Substances consists of two substantially different molecular weights and an HLB value within the range from 12 to 17, while a third substance has an HLB-tfert within the range from 1 to 5. 10. Composition according to claim 9, characterized in that each of the surface-active substances has a hydrophobic poly (propylene) core and hydrophilic polyoxyethylene units grafted onto it, and that one of the surface-active substances has a wetting agent with an HLB-fourth within the range of 1 to 5, a second a Eeinigungsmittel having an HLB value within the range of 12 to 17t ^e i ^ne third an emulsifier having an HLB value within the range of 12 to 17 and a fourth, a dispersant having an HLB of at least Mert 17th 11. Composition according to claim 8, 9 or 10, characterized in that it contains a sufficient amount of a strong acid, to provide the 1 to 5 parts by weight of available hydrogen ions able to contain a wetting agent, a cleaning agent and a sufficient amount of an emulsifying agent that 150 parts able to emulsify ligroin. 909829/1294 BATH ORIGINAL 12. Composition according to claim 8, 9, 10 or 11, characterized in that si e contains a cationic surface-active substance which is a fatty or oleamide modified with ethylene oxide, such as coconut oil amide or hydrogenated tallow amide. 13 · Process for the production of a water-soluble degreasing, oxide layer removal and dirt removal compound for Use in the process of claim 1, characterized in that a water-soluble mixture of a coordinated surface-active composition, an acid suitable for removing metal oxides and an inhibitor for inhibiting hydrogen embrittlement is mixed together, the surface-active Mass is able to perform the combined functions of metal wetting, oxide layer removal, oil emulsification and dirt dispersion 14. The method according to claim 13, characterized in that that the surface-active composition consists of a variety of surface-active substances, two of which are substantially different molecular weights and an HLB value within the Range from 12 to 17, while a third surfactant has an HLB value within the range has from 1 to 5 * 15. The method according to claim 13 or 14, characterized in that it uses a dispersant with an HLB value of at least 1? having· - 909829/3294 BAD ORIGINAL M 1668 16 «Procedure according to claims 13, 14 or 15, thereby characterized in that each of the surface-active substances has a hydrophobic polyoxypropylene core and is grafted thereon Has polyoxyethylene units, and that one of the surface-active substances is a final agent with an HLB value within the range of 1 to 5, a second a reliever with an HLB value within the range of through 17, a third an emulsifier having an HLIMert within the range of 12 Ms 17 and a fourth a dispersant with an HLB value above 17. 17 * Method according to claim 13, 14, 15 or 16, characterized in that the mass has a sufficient amount of a strong acid capable of delivering 1 to 5 parts by weight of available hydrogen ions, a wetting agent, a cleaning agent and contains a sufficient amount of an emulsifying agent, which is capable of emulsifying 150 parts of mineral spirits. 18. The method according to claim 13, 14 or 15, characterized in that a cationically surface-active Incorporated substance which is an ethylene oxide modified oil or fatty amide, such as coconut oil amide or hydrogenated Tallow amide. ? 9 • it Ci AV '-' { . »