IL28861A

IL28861A - Process for the pre-treatment of iron and steel before phosphatisation with manganese phosphate solutions

Info

Publication number: IL28861A
Application number: IL2886167A
Authority: IL
Original assignee: Metallgesellschaft Ag
Priority date: 1966-11-30
Filing date: 1967-10-31
Publication date: 1971-02-25
Also published as: ES347666A1; FR1531888A; GB1137449A; CH488029A; DK133957C; BE702536A; AT275263B; NO118524B; DE1521889B1; DK133957B; DD63687A5; NL6716053A; SE339900B

Description

PATENT ATTORNEYS PATENTS AND DESIGNS ORDINANCE SPECIFICATION Process for the of iron and steel before phosphatleation wit manganese phosphate solutions an of Frankfurt Germany do hereby declare the nature of this invention and in what manner the same is to be to be particularly described and ascertained in and by the following The manner in which manganese phosphate layers form on steel in the proeess of phosphatising in acidic aqueous manganese phosphate solution is largely dependent on the of the steel parts in aqueous solutions of strongly alkaline cleansers produce exceedingly layers which are liable to have large faulty areas lacking a coherent crystalline coat even after a protracted phosphatising of the metal parts in hydrochloric or furic acid equally favours the production of Against uniformly covering layers are obtained if the metal surface is degreased with an organic unfavourable effect of a treatment in strongly alkaline or strongly acidic are dried aqueous solutions can be eliminated in that the an intermediate drying operation after rinsing with then the parts are treated with organic solvents and only thereafter A further countermeasure consists in that the fter with alkaline solutions or are wiped with a rag after being rinsed with The coatings formed on the wiped areas are almost without exception very fine fine crystalline dense covering layers are formed on areas treated by other mechanical by sandblasting or by means scouring the need has been felt for a long time to provide a method which combines the thorough oxide dissolving property of acidic pickling solutions with the advantage of the mechanical enhancing of the formation of fine covering manganese phosphate The attempt of having recourse to the working manner known for phosphatisation by means of zinc phosphate the intermediate rinsing of the steel after the alkaline degreasing or with aqueous solutions containing condensed oxalic titanium phosphate and the did not have the desired does in alkaline permanganate solutions have completely satisfactory results in the long It has now been in accordance with this that unobjectionable manganese phosphate layers can be produced on iron and steel even after an alkaline if before the ing operations the pieces are contacted with an aqueous solution in which difficultly soluble phosphate is finely As difficultly soluble manganese orthophosphates for are suitable which are formed by the neutralisation of manganese phosphate solutions containing phosphoric to a of by means of in which process the acid may be added to the alkali or vice Other processes start from a ganese salt solution and effect the precipitation of manganese phosphate by the addition of The molar ratio of to in the precipitate is essentially determined by the conditions of the cipitation and can he for between 1 mole of to of of The effect of the according to the invention depends clearly on the crystal structure of the dispersed manganese Especially good results are achieved if at least one part Of the manganese phosphate is present in the form of fact that this is so can easily be proved by known methods such as Scherrer The with containing manganese phosphate in the subsequent phosphatisation by means of manganese fine crystalline manganese phosphate layers in frequently no crystals can be discerned any longer by the naked activating effect of the manganese phosphate is on its particle size and increases with increasing fineness of Very good results have been for by means of manganese phosphate of which about had a particle size smaller than and about were comprised in the particle size range below Satisfactory results achieved even with manganese phosphates having somewhat coarser The amount in which the manganese phosphate is used depends on the desired extent of refining of the layer and may be comprised within the region from a few milligrams per litre to about 5 Higher contents do not as a rule produce a further improvement but rather tend to have undesirable results in that larger amounts of sludge are deposited on the Of decisive importance for the efficaclty of the operation according to the invention is a degree of dispersion as possible of the manganese phosphate in the It is advisable to disperse the manganese in the bath with intense and also thereafter to keep the bath in strong movement as quently as by recycle pumping or of compressed In order to achieve as high a degree of dispersion as possible and to prevent too rapid depositing of the manganese the addition of alkali metal pyrophosphate to the bath has proved to be Preferred for this purpose is tetrasodium possibly in mixture with use of metal pyrophosphate by itself is not since owing to its low pH value this is apt to initiate a phosphate layer formation already in the which severely interferes with the layer formation proper in the manganese phosphate More highly condensed are considerably less efficacious than The pyrophosphate content of the bath is ferably from to 5 The to the bath favourably influences the stability of the The bath according to the invention soluble orthophosphate calcium These additions enhance the formation of a fine crystalline manganese phosphate Similarly as with manganese the efficacity of these additives increases with decreasing grain Iron orthophosphate calcium pyrophosphate may be added to the bath in amounts a few milligrammes per litre to about 5 The bath according to the invention can be applied by flooding or spraying at temperatures comprised between room temperature and As a no rinsing with water need be effected any lo between the and phosphatising though such intermediate rinsing does not substantially impair the For the subsequent manganeser phosphatising all known processes are They are used by but flooding or spraying can also produce objectionable The process according to the invention is strated by the following Samples sheets of quality 1405 m and hardened steel in various ways and subsequently phosphatised in a manganese phosphate In detail the following operations were by means of immersion for 5 at 25 of Pickling in sulfuric 150 of 3 of pickling inhibitor in immersion for 10 at Ringing in cold water Rinsing in hot water 2 of of of containing particle size in immersion for 1 at the bath was 2 of in 2 of immersion for 1 at the bath was of in 2 immersion for 1 at the bath was of in of pyrophosphate 2 of immersion for 1 at the bath was of of of of in immersion for 10 at The several experiments with their operations and the results obtained thereby are tabulated in the The favourable effect of the according to the invention is clearly recognisable by a comparison of the results of Experiment 2 with those of Experiments 3 and of 7 with those of Experiments 8 to Sheets and cogs showed in all cases virtually the same behaviour as regards the appearance of their surfaces afte the insufficientOCRQuality

Claims

CLAI S

1. A process for the pre-treatment of iron and steel surfaces before their being subjected to phosphatisation with manganese phosphate solutions, wherein the pieces a re contacted with an aqueous pre-rinsing solution containing finely dispersed difficultl soluble manganese-II-orthophosphate.

2. A process according to Claim 1, wherein a manganese-II-orthophosphate is used which consists at least in part of hureaulite.

3. · A process according to Claim 1 or 2, wherein an alkali metal pyrophosphate is added to the pre-rinsing solution.

4. A process according to Claim 1, 2 or 3» wherein difficultly soluble iron orthophpsphate is added to the pre-rinsing solution,

5. A process according to any of Claims 1 to 4» wherein difficultly soluble calcium pyrophosphate is added to the pre-rinsing solution.

6. A process according to any of Claims 1 to 5, wherein a tenside is added to the pre-rinsing solution.

7. A process according to any of Claims 1 to 6, wherein at least a portion of the difficultly soluble manganese-II-phosphate is present in a particle size smaller than 5

8. Processes for the pre-treatment of iron and steel surfaces prior to phosphatisation with manganese phosphate solutionst substantially as described herein.

9. Pre-rinsing eolutions for carrying out the processes, according to any of Claims 1 to 8, characterised by containing finely-dispersed difficultly soluble manganese-II-orthophosphate and if desired an alkali metal ro hoshate and or a 28861/2 10 - difficultly soluble iron orthophosphate and/or a diff cultly soluble calcium pyrophosphate and/or a tenside.

10. Iron and steel pieces having their surfaces phosphatised by the processes according to any of Claims 1 to 8. For the Applicants DR. REDJHOLD fiOSS AiiD PAR3JKSRS