EP0029418B1 - Procédé de découpage de fer et d'alliages de fer et composition pour la mise en oeuvre de ce procédé - Google Patents

Procédé de découpage de fer et d'alliages de fer et composition pour la mise en oeuvre de ce procédé Download PDF

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Publication number
EP0029418B1
EP0029418B1 EP80850166A EP80850166A EP0029418B1 EP 0029418 B1 EP0029418 B1 EP 0029418B1 EP 80850166 A EP80850166 A EP 80850166A EP 80850166 A EP80850166 A EP 80850166A EP 0029418 B1 EP0029418 B1 EP 0029418B1
Authority
EP
European Patent Office
Prior art keywords
acid
pickling
phosphoric acid
mole per
mol
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP80850166A
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German (de)
English (en)
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EP0029418A1 (fr
Inventor
Rune John Valdemar Niklassson
Peter Emanuel Nobel
Rolf Olof Nilsson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Boliden AB
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Boliden AB
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Filing date
Publication date
Application filed by Boliden AB filed Critical Boliden AB
Priority to AT80850166T priority Critical patent/ATE10016T1/de
Publication of EP0029418A1 publication Critical patent/EP0029418A1/fr
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Publication of EP0029418B1 publication Critical patent/EP0029418B1/fr
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/083—Iron or steel solutions containing H3PO4

Definitions

  • the present invention relates to a method of acid pickling metallic material having an iron content of at least about 80 per cent by weight, while simultaneously inhibiting exposed metal surfaces against acid attack.
  • the invention also relates to a pickling composition for carrying out the method containing phosphoric acid and one or both of the mineral acids hydrochloric acid and sulphuric acid and having a total acid concentration 0.5-2 mol/I.
  • Iron and steel works and manufacturing industries use acid pickling processes in the surface treatment of articles of iron, steel and other iron alloys.
  • pickling is primarily carried out to remove scale and other oxide and hydroxide layers which have formed on the metal surfaces of the articles during production. These layers are formed primarily when the articles are treated thermally, e.g. when annealed and subsequently rolled.
  • pickling processes are applied for the purpose of removing rust and other impurities from the surface of the material.
  • Rust is formed during the transportation, storage and handling of the metal articles, these articles comprising finished goods from the steel industry or intermediate products from other metal working industries, e.g. from sub-contractors.
  • the impurities originate from the same sources and may comprise, for instance, welding, soldering or brazing residues and handprint, although they may also be in the form of oil coatings and the like from processing operations or oil which has been purposely applied to protect the material against corrosion.
  • the acid solution used to pickle non-alloyed steels or low-alloy steels is mostly a sulphuric acid solution or a hydrochloric acid solution.
  • the acid solution used is mostly a nitric acid solution or a hydrofluoric acid solution, or a mixture of these two acids.
  • the acid used for pickling purposes in the manufacturing industry is predominantly sulphuric acid, although hydrochloric acid, nitric acid and hydrofluoric acid may also be used when considered an advantage in view of prevailing circumstances.
  • Phosphating - a chemical pre-treatment process in which there is preferably used solutions whose major component is either iron phosphate or zinc phosphate - is often used, however, to obtain a short time corrosion protection prior to finally treating an article, and to provide better adhesion surfaces for paints and varnishes applied to the article, thereby to improve the anti-rust properties of the finished surfaces.
  • the pickling time for removing rust is normally from 5 to 20 minutes.
  • a common feature of all pickling processes is that as soon as the base metal is exposed, it is attacked by the acid and dissolves, resulting in an unnecessary loss of metal. To avoid this there is normally added an organic inhibitor, which is adsorbed on the exposed surfaces of the metal to block the same, thereby protecting said surfaces against acid attack.
  • phosphoric acid primarily for special pickling processes, for intensified pickling processes and for pickling special metals, where the disadvantages associated with the use of phosphoric acid as a pickling agent can be accepted in view of the special application.
  • SU-A-152603 teaches the use of an acid pickling solution comprising a mixture of phosphoric acid and hydrochloric acid for the precision- pickling of iron metals, whereat the phosphoric acid content is 50 per cent by weight or more of the total acid content. It is proposed to recover the phosphoric acid content with the use of ion- exchanging resins, which is, of course, a very expensive method.
  • US-A-1 279 331 suggests the use of a mixture of phosphoric acid and sulphuric acid when pickling iron and steel.
  • the phosphoric acid content is more than 50 mole per cent by weight of the total acid content.
  • the stated purpose of the phosphoric acid addition is to avoid subsequent attack by rust.
  • the FR-A-2208006 also proposes a pickling solution containing phosphoric acid together with hydrochloric acid and sulphuric acid, whereat contents of 1-99 mole per cent by weight phosphoric acid, 5-99 mole per cent by weight sulphuric acid, and 5-99 mole per cent by weight hydrochloric acid are proposed as a pickling agent for stainless steel, and particularly as an agent to passivate such steels. Also JP-A- No. 53-138928 discloses stainless steel pickling compositions containing phosphoric acid.
  • the admixture of minor quantities of phosphoric acid with pure or mixed concentrated mineral acids, such as sulphuric acid, hydrochloric acid and nitric acid, has also been proposed.
  • the phosphoric acid is said to have a passivating effect on the acid, and its use is proposed in connection with acids which remain in contact with metal surfaces over very long periods of time.
  • the method can be considered as a phosphating method in situ.
  • a method for pickling soft carbon steel it is proposed in DE-B-1 169251 that the steel is treated with a solution containing sulphuric acid and/or phosphoric acid and hydrogen peroxide.
  • the phosphoric acid content is said to be 80-95 per cent by weight of the total acid content.
  • Phosphoric acid additions as pickling agents are also proposed in GB-A-854588, whereat the pickling agent, which may be in liquid or paste form, also includes sulphuric acid, hydrochloric acid, oxalic acid or an oxalic acid salt, a chromium salt and a wetting agent.
  • the pickling agent which may be in liquid or paste form, also includes sulphuric acid, hydrochloric acid, oxalic acid or an oxalic acid salt, a chromium salt and a wetting agent.
  • the method is considered particularly suitable for cleaning metal surfaces which are to be painted. In such applications factors concerning pickling times and the dissolving of metals are not important and have not been discussed in the publication.
  • FR-A-1236268 a mixture of hydrochloric acid, phosphoric acid and sodium borate can be used for rapidly pickling iron metals.
  • the pickling time is relatively long and the phosphoric acid addition relatively high.
  • CH-A-134632 it has also been proposed to use phosphoric acid as a pickling agent at elevated temperatures and pressures, in order to achieve satisfactory pickling times and results.
  • the use of phosphoric acid as a pickling agent either alone or in combination with other pickling acids, is well known to the art. It will be noted however, that in all cases the acid has been used despite those problems which it can cause.
  • phosphoric acid as a pickling agent can be considered known in extreme cases as an extreme measure, where extreme requirements are placed on the appearance of the surfaces of a workpiece subsequent to pickling and treating the same, and where a residual protective surface is required (phosphating effect).
  • the correct pickling time is chosen. If the time chosen is too short, the result may be an incompletely cleansed surface, which may provide a product of poorer quality and render the surface more liable to corrosion later on.
  • the pickling time chosen is, on the other hand, too long, the amount of acid and steel consumed is greater than necessary. Moreover, in this latter case the structure of the steel surfaces becomes coarser, the useful lifetime of the bath decreases, and the load on the surroundings resulting from the vapours given off from the bath increases.
  • the pickling process could be made less sensitive to variations in pickling times.
  • the acid By controlling the process, it would be possible to utilize the acid more effectively, to reduce the energy consumed, to produce a product of more uniform quality, and to reduce the number of interruptions in production caused by bath changes.
  • the pickling process can be divided into two stages. In the first stage, a major part of the scale present on the surfaces of the articles is quickly dissolved. The remainder of the scale is dissolved in the second stage, while the dominating part of the process is an attack on the cleansed metal surfaces exposed by the removal of the scale.
  • the two stages in the pickling process can be separated specifically, if the decrease in weight per unit of time is determined as a function of the pickling time. During the second stage, it is also possible to observe the generation of hydrogen gas in a quantity corresponding to the amount of pure metal dissolved.
  • pickling processes using hydrochloric acid are effected at lower temperatures than those using sulphuric acid.
  • scale and pure metal are dissolved more rapidly than in sulphuric acid.
  • the pickling rate in a hydrochloric bath is very high, especially when Fe 2+ ions are already found in the bath at the commencement of the process.
  • the said second stage of the process is also effected much more slowly in phosphoric acid, which can be attributed to the formation of iron phosphate on the exposed metal surfaces.
  • Phosphoric acid differs advantageously from both sulphuric acid and hydrochloric acid in this way.
  • a prime object of the present invention is to provide a method of overcoming the aforementioned disadvantages while substantially fulfilling the aforeindicated desiderata. It has been found possible to achieve this object by using a pickling bath comprising novel, specific combinations of pickling acids.
  • Another object of the invention is to provide a method in which the oxide layer, in the form of scale on rust, partially or completely covering the surfaces of the article, is rapidly dissolved.
  • a further object of the invention is to reduce the extent to which metal is undesirably dissolved with extensive pickling times. This can be achieved by blocking the pure metal surfaces against the attack of hydrogen ions in the acid solution.
  • Yet another object is to facilitate further surface treatment of the articles in conjunction with the pickling process, so that said surfaces can, for example, be pre-treated before applying thereto, e.g. a coating of paint or varnish, or some other layer forming organic substance.
  • the present invention which relates to a method and an improved pickling agent for pickling articles of iron and iron alloys of before mentioned kind.
  • the method of the invention is characterized in that said material is brought into contact with an aqueous solution containing phosphoric acid and one or both of the mineral acids hydrochloric acid and sulphuric acid, whereat the amount of phosphoric acid in the solution is adjusted to at least 0.1 mol/I and at most 1 mol/I, and the total acid concentration is 0.5-2 mol/I.
  • the agent for carrying out the method is characterized in that it includes, as an inhibitor, phosphoric acid in an amount of at least 0.01 mol/I and at most 1 mol/I.
  • the lower limit for the phosphoric acid content in the pickling solution is 0.01 mol/I. If the content is not maintained in the solution a substantial greater attack on the base metal will occur, which is not desirable. When the phosphoric acid content exceeds 1 mol/I the scale dissolution on the other hand will be so slow that the pickling time would have to be extended to an essential extent. This will decrease the pickling capacity and thus also the pickling economy. It is also essential in the method that the total acid concentration is controlled to be within the range of 0.5-2 mol/I. A lower total acid concentration will also give unacceptable long pickling times which results in serious disadvantages of beforementioned type.
  • the rate at which the metal is dissolved is low and remains unchanged when the phosphoric acid content is at least 0.2 M, corresponding to 10 mole per cent of the total acid present. When the phosphoric acid content falls below this level, the rate at which the metal dissolves increases.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Polishing Bodies And Polishing Tools (AREA)
  • Luminescent Compositions (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)

Claims (3)

1. Procédé de décapage par acide de matières métalliques ayant une teneur en fer d'au moins environ 80% en poids, tout en inhibant en même temps une dissolution provoquée par l'attaque d'acide des surfaces métalliques mises à nu, caractérisé en ce qu'une telle matière est amenée en contact avec une solution aqueuse contenant de l'acide phosphorique et un ou les deux acides minéraux formés par l'acide chlorhydrique et l'acide sulfurique, de manière que la quantité d'acide phophorique dans un système d'acide phosphorique et d'acide chlorhydrique soit de 0,1 mole/I à 0,05 mol/I et soit comprise entre 5 et 20 moles % du total d'acide présent, et de manière que la quantité d'acide phosphorique dans un système d'acide phosphorique et d'acide sulphurique soit comprise entre 0,01 mole/I et 0,5 mol/I et aille jusqu'à 20 moles % du total d'acide présent, la concentration totale en acide étant ainsi de 0,5 à 2 moles/I.
2. Agent de décapage pour la mise en oeuvre du procédé suivant la revendication 1, comprenant un ou les deux acides minéraux formés par l'acide chlorhydrique et l'acide sulfurique et ayant une concentration totale en acide d'environ 0,5 à 2 moles/I, caractérisé en ce qu'il comprend, comme inhibiteur, de l'acide phosphorique en une quantité d'au moins 0,01 à 0,5 mole/I, de sorte que, dans un système d'acide phosphorique et d'acide chlorhydrique, l'acide phosphorique soit présent à raison de 5 à 20 moles% de la concentration totale d'acide présent, et de manière que, dans un système d'acide phosphorique et d'acide sulfurique, l'acide phosphorique soit présent en une quantité allant jusqu'à 20 moles % de la concentration totale en acide.
3. Agent de décapage suivant la revendication 2, caractérisé en ce qu'il contient également des ions de fer (II).
EP80850166A 1979-11-06 1980-11-05 Procédé de découpage de fer et d'alliages de fer et composition pour la mise en oeuvre de ce procédé Expired EP0029418B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT80850166T ATE10016T1 (de) 1979-11-06 1980-11-05 Verfahren zum saeurebeizen von eisen und eisenlegierungen und zusammensetzung zur durchfuehrung des verfahrens.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE7909187 1979-11-06
SE7909187 1979-11-06

Publications (2)

Publication Number Publication Date
EP0029418A1 EP0029418A1 (fr) 1981-05-27
EP0029418B1 true EP0029418B1 (fr) 1984-10-24

Family

ID=20339264

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80850166A Expired EP0029418B1 (fr) 1979-11-06 1980-11-05 Procédé de découpage de fer et d'alliages de fer et composition pour la mise en oeuvre de ce procédé

Country Status (8)

Country Link
EP (1) EP0029418B1 (fr)
JP (1) JPS56501490A (fr)
AT (1) ATE10016T1 (fr)
DE (1) DE3069514D1 (fr)
DK (1) DK289081A (fr)
FI (1) FI68865C (fr)
NO (1) NO812196L (fr)
WO (1) WO1981001298A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2288190A (en) * 1994-04-08 1995-10-11 Wonder Wheels Cleaning composition containing hydrochloric acid
US6420178B1 (en) * 2000-09-20 2002-07-16 General Electric Company High throughput screening method, array assembly and system
US10450668B2 (en) 2017-04-11 2019-10-22 Savannah River Nuclear Solutions, Llc Development of a passivated stainless steel surface
CN108930043A (zh) * 2018-08-15 2018-12-04 东莞市同盛电子科技有限公司 一种去除金属氧化层的清洗剂及其制备方法和使用方法

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU152603A3 (fr) * 1900-01-01
US1279331A (en) * 1918-05-11 1918-09-17 James H Gravell Pickling iron and steel.
US2559445A (en) * 1946-12-12 1951-07-03 Union Switch & Signal Co Method for removing scale from steel
FR1148779A (fr) * 1956-02-01 1957-12-13 Procédé de protection des métaux contre la corrosion par les acides forts et compositions pour la mise en oeuvre de ce procédé
US2923608A (en) * 1956-04-13 1960-02-02 Fmc Corp Method of improving the bonding properties of steel surfaces
BE579543A (fr) * 1958-06-19
US3438799A (en) * 1965-06-22 1969-04-15 Chem Eng Ltd Method for the surface treatment of metal articles
US3457107A (en) * 1965-07-20 1969-07-22 Diversey Corp Method and composition for chemically polishing metals
BE740608A (en) * 1968-10-22 1970-04-01 Metal cleaning and protection process
BE790538A (fr) * 1971-10-26 1973-02-15 Ericsson Telefon Ab L M Bain de nettoyage chimique d'aluminium
FR2208006A1 (en) * 1972-11-24 1974-06-21 Produits Ind Cie Fse De-passivation of stainless steel - prior to plating or coating with copper, nickel, chromium, zinc, manganese, oxalate or phosphate

Also Published As

Publication number Publication date
WO1981001298A1 (fr) 1981-05-14
DE3069514D1 (en) 1984-11-29
JPS56501490A (fr) 1981-10-15
ATE10016T1 (de) 1984-11-15
DK289081A (da) 1981-06-30
EP0029418A1 (fr) 1981-05-27
FI812107L (fi) 1981-07-03
FI68865C (fi) 1985-11-11
NO812196L (no) 1981-06-26
FI68865B (fi) 1985-07-31

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