Cadmium Substitution - garteur

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GARTEUR LIMITED Coating Dry After immersion 1 ED cadmium passivated painted 0.3 0.3(0.5) 2 ED cadmium vapour degrease + painted 0.1 0.1 passivation 3 ED zinc-cobalt iron passivated painted 0.4(0.8) 1.1 4 ED zinc-nickel passivated painted 0.2 0.8(1.1) 5 ED zinc-nickel vapour degrease + painted 0.1 0.1 passivation 6 Sermetel 984/985 solvent wipe painted 0.2 1.1 7 Sermetel 984/985 light abrasion + painted 0.2 1.1 solvent wipe Table H3; Results of cross cut tests Page 96 GARTEUR SM/AG17 TP128
GARTEUR LIMITED ANNEX I Tribological properties I.1 Introduction The tribological properties of the coatings are an important consideration when used on fasteners or on threaded parts. In the tightening up of a bolt most of the effort expended is used in overcoming the frictional constraints. <strong>Cadmium</strong> has a low coefficient of friction (~0.2) so that a comparatively low torque need be applied to achieve a given level of preload. During the assembly of aircraft structures it is often necessary to bolt parts into place and then remove them to make adjustments or modifications. This process may be repeated several times and it is important that the torque-tension characteristics of the coated bolts used remain unaltered. In order to determine the suitability of the different coatings for use on fasteners the current programme has determined the coefficient of friction of several of the coatings and has compared the torque-tension characteristics of coated fasteners after repeated tightening and untightening. I.2 Torque - tension measurements I.2.1 Hi-Lok fasteners Two systems were evaluated:- (1) steel pins and steel collars (2) titanium pins and steel collars For each system the preload obtained and the locking torque was recorded. Tables I1 and I2 summarise the data for tests made on steel and titanium pins respectively. The figures given represent the average of 7 measurements. The results obtained indicate that the level of preload and locking torque values are dependent on the coating system. The normal requirement is that the preload should be in the range 4 to 9kN. As indicated in tables I1 and I2 the minimum preload of 4kN was exceeded with all of the coatings examined. I.2.2 Coated steel bolts Results of the torque - tension tests conducted by SAAB on steel bolts and nuts coated with cadmium and various alternative coatings are given in table I3. Data are also included in the table previously obtained at SAAB [I1] and at DERA [I2,I3]. I.3 Reusability tests Tests were made to determine the effect of repeated tightening up and untightening on the performance of coated nuts and screws. The work undertaken by DBAA has concentrated on fasteners coated with cadmium and Delta-tone. Data obtained are presented in figure I1 showing the effect of repeated loading and unloading on the coefficient of friction (μ). Different combinations of cadmium and Delta-tone plated steel bolts and nuts have been examined. The results indicate that when the bolt and nut are both cadmium plated there is an increase in the coefficient of friction as the combination is repeatedly tightened and untightened. When either the nut or bolt is coated with Deltatone there is only a small change in the value of μ. Data are presented in figure I2 showing the effects of repeated loading on the preload to torque-off ratio. This shows that the largest decrease occurs with the cadmium plated bolt-cadmium plated nut combination. GARTEUR SM/AG17 TP128 Page 97
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GARTEUR LIMITED As plated Passivate
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GARTEUR LIMITED A.2.4 Delta-tone/De
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GARTEUR LIMITED 1 Abrasive blast us
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Page 66 and 67: GARTEUR LIMITED Type A Measurements
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Page 118 and 119: GARTEUR LIMITED Cadmium coated bolt
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Cadmium Substitution - garteur

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