DE1521160A1 - Corrosion-resistant coatings for iron and processes for their manufacture - Google Patents

Description

Corrosion-resistant covers for Lisen and Yer to make them The invention relates to zinc-aluminum- @ berzüle for iron, and in particular on a zinc-aluminum coating that is corrosion-resistant and ductile and adheres extremely well to the surface of the steel.

To protect the surface of iron against corrosion, is It is common to have the iron on its surface with a coating of non-ferrous metal to cover. for this one can put the iron object in a molten bath from this Immerse non-ferrous metal. Other coating processes are also known. Such Coating on biscuits is not only intended to protect iron against corrosion. They should also be equally ductile, adhere well to the iron and also absorb convey a pleasing appearance. Non-ferrous metals previously used in the production of Coatings used in industry are, for example, aluminum, zinc and tin or letter metal, as coatings made from these metals have very favorable properties and can be easily manufactured.

As the cost of making uppers from aluminum and from Zinc are relatively low, such coatings are often used to protect Iron or steel items used against atmospheric corrosion. Zinc coatings give iron or steel also a galvanic protection, so that the corrosion resistance of iron or steel is increased even if part of the coating is missing or disappeared _i st. Aluminum, like zinc in the electrochemical series above yisen, steel can work under all atmospheric conditions galvanj # Ch do not protect. This is due to the oxides that are on the market Form aluminum surfaces. Even so, for some purposes, aluminum coatings are great useful because an aluminum coating is quite resistant to corrosive atmospheres iät. Coatings made of aluminum-zinc ornaments; ., iron b <: stirru: @te that their use is cheaper than the use of coatings Make zinc or aluminum appear on their own -zilleine. It is therefore often desirable Manufacture Lc_erzüL.e from such-aluminum-zinc alloys. It is known, band material made of iron with @. a zinc-ll uminiur :: - decoration with a -9sluminilungel_alt between 5 and "G" i "evjic: hts percent to be drawn Procedure be.t-.nd in it, on the candr: a t, erial from t; isen zue.L st a coating Abis to apply zinc, then pass the jandL: aterial through a and it at the end of an ac: "relzbad Abis einet 'to expose aluminum-zinc alloy. In this process, however, lead dissolves in the subsequent alloy bath within a narrow range of at least 1 p, so that: ß the subsequently produced coating Made of aluminum-oink alloy t @@ e :: @ t'alls a lead content of at least 1> identifies. : This lead content affects the corrosion resistance of the Lberzuges in a high degree. There is therefore a need to use iron or ätuhl with tiner = i ink-aluminum coating high corrosion resistance to remove its lead content can be closely monitored. In particular, there is a need for a zinc-Xluninium-u -Erzug, which is metallurgically built on the iron or on the steel, so that this coating is ductile and adheres well to the yisen ouer am atanl. It has turned out that üink alurainium coatings, which have a noticeable lead content, have a low level Have corrosion resistance. -uie -x-irfindung, on the other hand, contains an ave - = ,, iiren, like the lead content in such an aluminum-zinc @ bez -zug over-. watch = and so can be kept low because: 3 There are no corrosion problems due to the lead content more surrender. -: - s new i ei «f; iiir enspi'oüu.: t consists of aL @ s r @ erniajaterial _ius l; isen, on which -: in üiilk-Aluininiuui-uberzug iaetallurisch is gebaiiaen. About the aluminum coating of the new process product shows one Alaminium content between 5 and 25 Geirieiitsi) - t.-oz, ducks on. Its lead content is very low.

In order to produce this process product, it is a pilaster article such as well cleaned rai-: ds-lahl in a melt pool from 2; ink-nluminiuni ein._etaucht, Giessen A-urziniur: salary; wipe 9> and 2590 lieL. »t, and the US still contains silicon in a length that is no smaller as et, y.0,5 ya the aluminiujii: @f: n-e used is.

The egg content of the bath is monitored and kept so low that ä; .ß an accelerated Kor :. osion does not change occurs to-; so ate himself up the surface of the coating does not form any hoi-i ° osionc .produi, te iäjehr that the Affect the quality of the coatings. # "iri -.- correct I" eri, -ii, al der # ürfindung Does it contain, di "= itself ü s 1 L? ' i ..-- itei ° ial and the A (r-ug at their .xz-enzl1, ciie behaves - slightly l: iiteii., other leg-.erer. Due to the - e--. ir: crkmals in with the already he - @, ztiaizten bigen # -chnften u.:=s: berzu, # -, est va-_e -buht: l.orrosion resistance and ductility @ is üie: Lrlinäung bcäon-: eru good for covering: von Bandst @ _hl; eei: net, although make other items from Bisen after four: i @ rfindunb can be coated, provided you put them in a Z-chirlelzba :. immerse i1 at i. .

The following will follow: rz = findun, in verbinäurg mi-u de-. Drawing described, Gie a scher: atic side view of a # Vorrichtuii` for guiding of the method according to the invention.

"In a preferred embodiment of the method: -hr @ .is after the rrfind @ in @ to cover a core made of pilaster strips, as in the case of the cover drawing of strip steel, the L: .i @ -: is-ahl is first followed by a -teiniguti: o-säau :: iizäulcli @ ef?: hrt, in which 2e-1, t, Ztaub unci ü (, "ir.ut vem tbeinU, stai: l are removed. The @ eäääuberte; .t71` äVl ''a in a @ Ctut @ ä @ tatrlol`i: az'e oi-; .. vif einc; 1'B? .`i "He _'tL_1' heated up, about over` 1'enil: eratur des Sc ., irle -_'_ zbci_des] and geüo @ en directly through the bath. The smelting bath made of zinc and aluminum has a kluminiurl #, held z "" ibclien 5 - and 25;, and still contains silicon in a lien @ The maximum lead content of the .3-, des is less than 0.65 , preferably less than 0.1 the melting point of the zinc-aluminum-T @: mixture and thus changes with the aluminum-green used.

j "-iclistelend- is to be described using a special example become like a coating on a steel strip according to the method of 1,; z @ findun4 ,; li @ can be created.

In the figure 1, steel strip 1 made of unoei-uhig-tem, itahl (thickness 28 gage = 0.4 mm thick) is fed from a supply roll 2 to a door 3 which contains the similar aqueous cleaning solution 4 The cleaning solution 4 consists of "Penns = _ @ lt lio. 30 "at a concentration of about 4 ounces per gallon (about 45 g / l). This is a common alkaline cleaning agent for metal surfaces. The cleaning bath 4 was maintained at a temperature between about 850 ° and y5 ° G. The cleaned The steel strip was then brushed off with brushes 5 and sept-1t in the rinsing tank 6 with the 7. Vc.m üpü: .tank 6, the steel strip was deflected over rollers 9 and passed through a Ufen 10, in which the steel was heated to a temperature of about 650o C. This furnace was heated with the combustion products of natural gas and air, which were fed to the furnace in a ratio of 1 to 8. From this furnace the steel strip was passed over another troll 11 and extended into a chamber 12 in which the temperature of the steel strip was lowered to about 425 ° C. In the chamber 12 there was an atmosphere of 99 "hydrogen, the task of which was to prevent the steel strip from oxidizing before the steel strip entered the fuselage tich 13 entered. Inside the melting tub 13, the steel strip was pulled through a molten bath 14 by means of two halls 15 and 15 '. The bath temperature was kept at about 5600 U. After leaving the bath, the steel strip was pulled between two smooth, Ya = _zen 16 made of steel with a low carbon content. After leaving the bath, the steel strip was then guided vertically upwards to the roller 18 and around this roller 18 to the winding roller 19. On the 'way to the deflection roller 18, the overflow was quenched by means of an air blower 17. The speed of the steel strip was about 14 tenants per minute and the immersion time in the melt was about 4 seconds.

To produce the weld pool, zinc with a purity of better than 99.99 96 was mixed with aluminum with a purity of> 99.5. The analysis of the aluminum would give the following result: Aluminum 99.65 Iron 0.19 Silicon 0.03 Manganese 0901 zinc 0.01, a Yanadium 0.01 Cadmium 0p02 A Sodium 0.001 p The silicon was added to the aluminum-zinc mixture in the form of a practically lead-free aluminum-silicon alloy with a silicon content of 12.

The individual components were added to the bath in proportions such that the analysis of the molten bath showed an aluminum content of about 12.8 %, a zinc content of about 86.7% and a silicon content of about 0.4%. The analysis of the Gberzüges, which was applied to the sand steel according to this example, had essentially the same y @ bnis. Well, if this little piece of iron is broken, zinc -; # lur :: iniur @ ioberzLie applied to steel w (: rä, sera A _-_ urciinluriigehalt within the entire range of 5; o to 2_) aluminum can run. The only thing that hiez @ .a rioti! Enüi # 7 7 is the change of the used aluminum undinkm: @n en. It is not necessary to start with 4luminiurü and pink of the degrees of unity given above. It i-, but gün-cj, when the Alurii: Iniun content äes S; rr: elzbaäes between>; 4 and 25% a, if the "siliconrnen, e in the melt pool at least 0.5 / u of the xluminiutlislr: etr @ '. yt and vrerin the aest consists essentially of finch.

The bath temperature is favorably chosen: in 450 0 to 30 ' Ü higher than the acl # irielztemp @ "r rur des .tades, which r: .it increase aeti tiluminiuir: content also rises.

The amount of silicon. In the S-, hnielzbad at least: 0,> ia. he amount of aluminum used. A Siliziui: i @ eh..lt from the employed .Amount of aluminum is cheaper. -3if i: if necessary one can sum the silicon; e also over it -, - add to that. The silicon in the weld pool causes the image imperfection to adhere well_ Coating, prevents: Formation of a pilaster alloy at the interface between Steel strip and coating or restricts such an alloy formation a minimum and also ensures that the alloy layer is thin and even is. In the coating produced by the method just described, silicon was also included.

According to previous observations, however, the silicon content of the The coating produced in this way has no influence whatsoever on the corrosion resistance, so that the diconium as the compensation of the transfer itself is insignificant. To @@ trposition The metallurgical bond between the coating and the steel strip carries the silicon however, to a large extent.

The process products according to the invention with a low lead Aluminum-zinc coating were subjected to @al,: - S @, r @ il: tests. It turned out -, at which they were superior to such objects, a-: i those a purely Galvinian coat of arms @ äfge @ -__ ücht was. Lisher @ ige Alurriiniur: i - ii: k-überz-U: ge contained: lead in quantities of 1; or more, like e: = already acquired :: ütex-t wurue. @: enn the "= leigehalt im Überzujjeäoch under 0, @ üf @ icht @@ c @ .n'ten; ° is kept, cfie objects provided with this type of transfer show good durability gety; enü: er -; ti @ Iossahurian corrosion.

The `.lei = ir.en -gberzü`e show inside .alb esair: ten _ -reiches . # ",: Yischen 5 yo and 25 io aluminum content a good corrosion resistance: if there is any evidence of it, the corrosion resistance of a coating from a bag: -ui-chen aluminum-zinc alloy (about 21; o to 23; o aluminum) less t iet. Here it is higher as the rate of corrosion. which lies next to cem #t; utectic in its percentage composition. : desonde7s good ßrgeonisse; were achieved with coatings with an aluminum content between 5 # 5 and t '-, Oii lay. Within this: range is the range between, u and 15; o before » to pull. .

xluininiuni-zinc-lberzäge according to who @Urfinaung v; rmi-uteln yisen too a galvanic protection, as is also the case for L: el ° z @ i @ E, those made of zinc exist alone.

Lie process products according to the:; invention were based on previous ones = # lle; friction produced in this way, dra.l3 country steel by a Gcht :: elze made of outer coating alloy hincurchgc-zo; en was. But this is not the only way to use steel strip to be covered with a coating of an aluminum-zinc alloy. -an can for example on one side or on both sides of a stainless steel a mixture of zinc and aluminum powder or a zinc-aluminum alloy powder with a Apply lead content of less than 0.6, o on the steel strip and then sintered, so that a low-lead zinc-aluminum coating formed on the steel strip biluet. In this case, Siliziuru is not required to produce the coating. With the coatings according to the invention can not only be provided with strip steel Examples of other items that can be coated just as well are steel wire, Bolts, nuts, washers and machine components called the covers the products of the process according to the invention essentially consist of the metals Zinc and aluminum. However, they can also contain other substances, provided such additional additives add to the novel and fundamental properties of the invention non-affect. It does not matter whether these other substances are only used as Impurities are present or deliberately added.

All percentages in the description and in the following claims, which relate to the weld pool or the individual components of the coating, are percentages by weight.

If in the following claims an aluminum content between 5% and 24 S is claimed, this should be understood to mean a range that extends up to reaches an aluminum content of 25> without, however, including this 25 io. Exactly the same should be done with an aluminum content between 5 ° and 'cO 7o respectively between 5; ö and 15 / o should be understood to be a range that extends to an aluminum content from 21 7o or from 16.> reaches.

Claims (7)

.Patent claims 1. Object made of iron with a ductile, well-adhering and corrosion-resistant coating that is metallurgically bonded to the iron, since --chg e- indicates that the coating consists of aluminum between 5> and 24 b, and that the remainder is zinc and that the lead content of the coating is less than 0.6%. 2. The iron article of claim 1; a d u r c h g e k a n n n z e i n e i n e t that the coating silicon in an amount contains which exceeds 0.5 26 of the amount of aluminum used. 3. Item off Iron according to claim 1 or 2, d u r eh g e n n n 2 e i o h n e t that the Silicon is an insignificant component of the coating. 4. Iron object, after one or more of claims 1 to 3, d u r c h g e k e n n n z e i c h n e t that the lead content of the coating is less than 0.1%. 5. Item off Iron according to one or more of claims 1 to 4, d u r c h g e k e n n n it is noted that the aluminum content of the coating is between 5 gb and 20%. 6. Article made of iron according to one or more of claims 1 to 5, d a d u r c h g e k e n n n z e i c h n e t,. that the aluminum content of the coating between 5% and 15; b liigt. 7. A process for the production of objects made of iron with ductile, well-adhering and corrosion-resistant coatings according to one or more of claims 1 to 6, characterized in that the iron objects are drawn or immersed through a molten bath, -whose aluminum content is between 5 @ and 24%, the lead content of which is below 0.6%, that contains silicon in an amount which exceeds 0.5% of the aluminum used, and the remaining component of which is zinc: B. ''; , characterized by the fact that from. oxides are removed from the surface of the iron article, that the coating is metallurgically bonded to the surface of the iron article, and that the alloy layer containing iron sera at the interface between the coating and iron is influenced so that this alloy layer becomes thin and uniform. 9. The method according to claim 7 or 8, characterized in that the lead content of the melt is below 0.1 26. 10. The method according to claim 7, 8 or 9, characterized by the fact that> 3 the aluminum content of the melt is between 5 7a and 20%. 1'1. Method according to claim 7, 8 or 9, characterized -k 9 nnzei.; This means that the aluminum content of the melt is between 5% and 15 70.