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Anodic Films on German Alloy Parts

Anodic Films on German Alloy Parts Workshop and Production Section AIRCRAFT ENGINEERING October, 1944 TABLE I AMPLES of anodically treated aluminium ANODIC FILMS OK SAMPLES TAKEN PROM GERMAN AIRCRAFT alloy parts have been taken from several German aircraft, chiefly from the airframes. Sample Date of These have been examined for typeand nature of Aircraft Component Material and relevant Appearance of Film Thickness in microns capture British Spec. the anodic films. In all, nineteen parts have been By By examined. The names of the parts, the aircraft chemical microscop­ from which they were taken, the appearance of the method ical method anodic films, .and the corresponding type of British 1 23.3.42 Ju.88A4 Strip stringer from wing ... Wrought Dural (5L3) … Smooth, yellow, bright 13 10 material are indicated in the attached table. 2 Hat section stringer, fuselage ,, ,, 5L 3 i» ii ii 9 7 ,, ,, Scratch tests and bend tests showed that the 3 Tapered root, wing spar ... Extruded ,, (6L1) … Dull deep yellow 13 13 ,, ,, 4 ,, Tapered T longeron, fuselage (6L1) I I ,, II ... 8 5 films were adherent, hard and brittle. The film on ,, 5 T section, main wing spar „ A1. Alloy the cock body (Item 19) was very hard. ,, ,, (DTD.364A) ,i pale greenish yell. 6 9 6 Oil pipe from fuselage Wrought Anticorodal ... Smooth, yellow, bright 18 15 ,, ,, 7 ,, Mounting ring, nose gun ... Cast Al. Alloy (9% Si ,, Chemical Tests 0-5% Co) Rough, dark, grey ... 10 IS Inner1—pale yellow ... 8 Do.217E2 12.2.-42 Oxygen bottle Wrought Dural (5L3) 5 7 Chemical tests were made on samples of the Outer—blue ... ,.. 6 7 films after removal of the films by scraping. Sulphate 9 7.2.42 Lower flange, rear wing spar Extruded Al. Alloy ,, (DTD.364A) Palo yellow 6-4 9 was detected in all the films except tha t on the cock 10 Fuselage skin Alclad Sheet (L38) I I . II ... ... 6-3 7 ,, body. Chromium was detected in all the yellow ,, 11 ,, Control tube Wrought Dural (5T4) Yellow 4-6 S-0 ,, films but not in the buff-coloured film on the cock Inner—pale yellow ... 12 Oxygen bottle „ .. (6L1) 7-5 ,, ,, — Outer—blue 8-0 body. I t is evident that all the films except that on 13 JU.88A4 18.1.43 Tapered compensating piece, the cock body had.been produced in sulphuric acid lower wing spar Extruded Dural (6L1) Yellow .• 7-5 baths and that the yellow films had been sealed in Bright yellow 14 Control tube Wrought Dural (5T4) 13-0 „ — . Pipe coupling Pale yellow Cast Al. Alloy (2% Mg.) IS 6-0 dichromate solutions. „ — Hose end fitting Wrought Dural (5T4) IB Very bright yellow ... 11-5 „ __ 17 Mc. 210 6.9.42 Circular plate, flexible tank Bright yellow orifice .. (SLli 6-4 9-0 Observations on Film Thickness Palo yellow 18 Control tube .. (5T4) 7-0 „ — Al. Alloy Casting 19 He. 115BB Cock body Observations on film thickness were made by (4-85% Mg. 1-11% Si) Buff 15 removal of the films by chemical means and by microscopic examination of transverse sections. microscopical method of observing the thickness of able that the D.C. sulphuric process known in A boiling solution of phosphoric and chromic anodic films on aluminium is generally considered Germany as the "Eloxal G.S." process had been acids was used as recommended by J. D. Edwards to be the best. The results obtained on the present used. Most of these films had been sealed by treat­ (A.S.T.M. Preprint No. 19, 1940), since sealed samples are given in the attached table. ment in dichromate solutions to provide increased films are not readily removed by cathodic treatment efficiency of protection. The thicknesses of the films, in hot chromic acid solution. The thickness of the 5 to 15rnicrons, are not unusual for films produced films was calculated from the loss in weight on Comments and Conclusions by this method.' The depth of colour of the yellow stripping. In the calculation of film thickness the films appeared to be roughly proportional to the density of the film was assumed to be 2·8. It is The anodic film on the cock body appeared not to have been sealed. thickness of the films. The films on the external known, however, tha t the density of anodic films on The film was very hard, was 15 microns thick, and surfaces of the oxygen bottles had not been sealed aluminium alloys varies with the conditions during appeared to have been produced by the "Eloxal by dichromate treatment but had been dyed blue. formation of the film, etc., and that the values ob­ GX" process; i.e. by D.C. treatment in an oxalic The film on the gun mounting ring casting was of tained in this way vary by ± 25 per cent from the acid bath. As the plug (steel) of the cock seats direct­ dark grey colour due to the aluminium alloy con­ actual values of film thickness. The results are given ly upon the light alloy body, a hard anodic film on taining a high percentage of silicon. in the attached table. the latter should be of advantage in this application. The conditions of operation for anodic treatment Transverse sections of the samples were prepared Part of the cock body was cleaned and re-treated in of aluminium aircraft parts in Germany are 15 to and the anodic films were examined microscopically. an 8 per cent oxalic acid bath at 60 volts, 18-20 deg, The examination revealed no unusual feature. The 20 amp. per sq. ft., 11 to 22 volts, 16 to 24 deg. C , C., 60 mins. The new film resembled the original and sulphate of aluminium content of bath, not one but was 22 microns thick. The anodic films on greater than 45 grammes per litre. Hot potassium • Report N.F.C. 9. Prepared by the Staff of the Metallurgy the other items examined had all been produced in dichromate solution (90-95 deg. C.) is used to seal Division, Royal Aircraft Establishment, for the Committee on sulphuric acid electrolytes. I t is therefore most prob­ Non-Ferrouj parts of Enemy Aircraft the films. Mechanically Lapped Plug Gauges Trade Publications Received An innovation in plug gauge manufacture is the Machining of Wrought Aluminium Alloys. introduction by the Newall Engineering Company Limited of mechanical lapping, for which outstand­ (W.L.A.D.A. Information Bulletin, No. 7.) ing advantages are claimed. In the past it has been [Wrought Light Alloys Development Asso­ accepted practice to grind plug gauges to final size ciation. Birmingham.] or, where an extra smooth finish was wanted, to use hand lapping. I t was recognized that hand lapping Tooling Economy was superior to grinding, as this refinement removed [Machine Tool Control, 35 Old Queen Street, chatter and other small imperfections unavoidable London, S.W.I.] in a ground finish'. The Newall Engineering Company always re­ "Delarmet" Bearings garded hand lapping as a step in the right direction and for a long time have been experimenting with [De La Rue Plastics Ltd. London.] the mechanical lapping of plug gauges. This has Aluminium al War. W. C. Devereux lead to the introduction of specially constructed machines (see Fig. 1), with the result that all [High Duty Alloys Ltd.. Slough.] Newall Plug Gauges in standard sizes from ¼ in. to 1½ in. diameter are now supplied mechanically The Fairey "Benfold" Machine lapped at no extra cost. [The Fairey Aviation Co. Ltd., Hayes.] An exhaustive series of tests has been carried out t o ascertain the relationship existing between the "Essex" Acetylene Oxygen Gas Economizer finish of a plug gauge and its length of life so far as [Motor Gear & Engineering Co. Ltd . Chadwell gauging accuracy is concerned. These tests have Heath.] proved conclusively that gauges with mechanically lapped surfaces have a considerably longer accurate Vokes Filters life than those finished by other processes. [Vokes Ltd. London.]' I t is also claimed that mechanically lapped gauges will remain within acceptable gauging tolerances Presswork for Manchester for approximately four times as long as hand lapped gauges. [Manchester Metal Works Ltd. Salford.] E. H. Jones (Machine Tools) Ltd., of Edgware X-Ray Darkroom Practice Road, The Hyde, Hendon, N.W.9, are the agents for all Newall gauges and will be glad to give further Lead Screens for Industrial Radiography information on this new development. [Ilford Ltd., London.] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

Anodic Films on German Alloy Parts

Aircraft Engineering and Aerospace Technology , Volume 16 (10): 1 – Oct 1, 1944

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb031181
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Abstract

Workshop and Production Section AIRCRAFT ENGINEERING October, 1944 TABLE I AMPLES of anodically treated aluminium ANODIC FILMS OK SAMPLES TAKEN PROM GERMAN AIRCRAFT alloy parts have been taken from several German aircraft, chiefly from the airframes. Sample Date of These have been examined for typeand nature of Aircraft Component Material and relevant Appearance of Film Thickness in microns capture British Spec. the anodic films. In all, nineteen parts have been By By examined. The names of the parts, the aircraft chemical microscop­ from which they were taken, the appearance of the method ical method anodic films, .and the corresponding type of British 1 23.3.42 Ju.88A4 Strip stringer from wing ... Wrought Dural (5L3) … Smooth, yellow, bright 13 10 material are indicated in the attached table. 2 Hat section stringer, fuselage ,, ,, 5L 3 i» ii ii 9 7 ,, ,, Scratch tests and bend tests showed that the 3 Tapered root, wing spar ... Extruded ,, (6L1) … Dull deep yellow 13 13 ,, ,, 4 ,, Tapered T longeron, fuselage (6L1) I I ,, II ... 8 5 films were adherent, hard and brittle. The film on ,, 5 T section, main wing spar „ A1. Alloy the cock body (Item 19) was very hard. ,, ,, (DTD.364A) ,i pale greenish yell. 6 9 6 Oil pipe from fuselage Wrought Anticorodal ... Smooth, yellow, bright 18 15 ,, ,, 7 ,, Mounting ring, nose gun ... Cast Al. Alloy (9% Si ,, Chemical Tests 0-5% Co) Rough, dark, grey ... 10 IS Inner1—pale yellow ... 8 Do.217E2 12.2.-42 Oxygen bottle Wrought Dural (5L3) 5 7 Chemical tests were made on samples of the Outer—blue ... ,.. 6 7 films after removal of the films by scraping. Sulphate 9 7.2.42 Lower flange, rear wing spar Extruded Al. Alloy ,, (DTD.364A) Palo yellow 6-4 9 was detected in all the films except tha t on the cock 10 Fuselage skin Alclad Sheet (L38) I I . II ... ... 6-3 7 ,, body. Chromium was detected in all the yellow ,, 11 ,, Control tube Wrought Dural (5T4) Yellow 4-6 S-0 ,, films but not in the buff-coloured film on the cock Inner—pale yellow ... 12 Oxygen bottle „ .. (6L1) 7-5 ,, ,, — Outer—blue 8-0 body. I t is evident that all the films except that on 13 JU.88A4 18.1.43 Tapered compensating piece, the cock body had.been produced in sulphuric acid lower wing spar Extruded Dural (6L1) Yellow .• 7-5 baths and that the yellow films had been sealed in Bright yellow 14 Control tube Wrought Dural (5T4) 13-0 „ — . Pipe coupling Pale yellow Cast Al. Alloy (2% Mg.) IS 6-0 dichromate solutions. „ — Hose end fitting Wrought Dural (5T4) IB Very bright yellow ... 11-5 „ __ 17 Mc. 210 6.9.42 Circular plate, flexible tank Bright yellow orifice .. (SLli 6-4 9-0 Observations on Film Thickness Palo yellow 18 Control tube .. (5T4) 7-0 „ — Al. Alloy Casting 19 He. 115BB Cock body Observations on film thickness were made by (4-85% Mg. 1-11% Si) Buff 15 removal of the films by chemical means and by microscopic examination of transverse sections. microscopical method of observing the thickness of able that the D.C. sulphuric process known in A boiling solution of phosphoric and chromic anodic films on aluminium is generally considered Germany as the "Eloxal G.S." process had been acids was used as recommended by J. D. Edwards to be the best. The results obtained on the present used. Most of these films had been sealed by treat­ (A.S.T.M. Preprint No. 19, 1940), since sealed samples are given in the attached table. ment in dichromate solutions to provide increased films are not readily removed by cathodic treatment efficiency of protection. The thicknesses of the films, in hot chromic acid solution. The thickness of the 5 to 15rnicrons, are not unusual for films produced films was calculated from the loss in weight on Comments and Conclusions by this method.' The depth of colour of the yellow stripping. In the calculation of film thickness the films appeared to be roughly proportional to the density of the film was assumed to be 2·8. It is The anodic film on the cock body appeared not to have been sealed. thickness of the films. The films on the external known, however, tha t the density of anodic films on The film was very hard, was 15 microns thick, and surfaces of the oxygen bottles had not been sealed aluminium alloys varies with the conditions during appeared to have been produced by the "Eloxal by dichromate treatment but had been dyed blue. formation of the film, etc., and that the values ob­ GX" process; i.e. by D.C. treatment in an oxalic The film on the gun mounting ring casting was of tained in this way vary by ± 25 per cent from the acid bath. As the plug (steel) of the cock seats direct­ dark grey colour due to the aluminium alloy con­ actual values of film thickness. The results are given ly upon the light alloy body, a hard anodic film on taining a high percentage of silicon. in the attached table. the latter should be of advantage in this application. The conditions of operation for anodic treatment Transverse sections of the samples were prepared Part of the cock body was cleaned and re-treated in of aluminium aircraft parts in Germany are 15 to and the anodic films were examined microscopically. an 8 per cent oxalic acid bath at 60 volts, 18-20 deg, The examination revealed no unusual feature. The 20 amp. per sq. ft., 11 to 22 volts, 16 to 24 deg. C , C., 60 mins. The new film resembled the original and sulphate of aluminium content of bath, not one but was 22 microns thick. The anodic films on greater than 45 grammes per litre. Hot potassium • Report N.F.C. 9. Prepared by the Staff of the Metallurgy the other items examined had all been produced in dichromate solution (90-95 deg. C.) is used to seal Division, Royal Aircraft Establishment, for the Committee on sulphuric acid electrolytes. I t is therefore most prob­ Non-Ferrouj parts of Enemy Aircraft the films. Mechanically Lapped Plug Gauges Trade Publications Received An innovation in plug gauge manufacture is the Machining of Wrought Aluminium Alloys. introduction by the Newall Engineering Company Limited of mechanical lapping, for which outstand­ (W.L.A.D.A. Information Bulletin, No. 7.) ing advantages are claimed. In the past it has been [Wrought Light Alloys Development Asso­ accepted practice to grind plug gauges to final size ciation. Birmingham.] or, where an extra smooth finish was wanted, to use hand lapping. I t was recognized that hand lapping Tooling Economy was superior to grinding, as this refinement removed [Machine Tool Control, 35 Old Queen Street, chatter and other small imperfections unavoidable London, S.W.I.] in a ground finish'. The Newall Engineering Company always re­ "Delarmet" Bearings garded hand lapping as a step in the right direction and for a long time have been experimenting with [De La Rue Plastics Ltd. London.] the mechanical lapping of plug gauges. This has Aluminium al War. W. C. Devereux lead to the introduction of specially constructed machines (see Fig. 1), with the result that all [High Duty Alloys Ltd.. Slough.] Newall Plug Gauges in standard sizes from ¼ in. to 1½ in. diameter are now supplied mechanically The Fairey "Benfold" Machine lapped at no extra cost. [The Fairey Aviation Co. Ltd., Hayes.] An exhaustive series of tests has been carried out t o ascertain the relationship existing between the "Essex" Acetylene Oxygen Gas Economizer finish of a plug gauge and its length of life so far as [Motor Gear & Engineering Co. Ltd . Chadwell gauging accuracy is concerned. These tests have Heath.] proved conclusively that gauges with mechanically lapped surfaces have a considerably longer accurate Vokes Filters life than those finished by other processes. [Vokes Ltd. London.]' I t is also claimed that mechanically lapped gauges will remain within acceptable gauging tolerances Presswork for Manchester for approximately four times as long as hand lapped gauges. [Manchester Metal Works Ltd. Salford.] E. H. Jones (Machine Tools) Ltd., of Edgware X-Ray Darkroom Practice Road, The Hyde, Hendon, N.W.9, are the agents for all Newall gauges and will be glad to give further Lead Screens for Industrial Radiography information on this new development. [Ilford Ltd., London.]

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: Oct 1, 1944

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