UNCLASSIFIED

AD 285 372

ARMED SERVICES TECHNICAL INFORMATION AGENCYARLINGTON HALL STATIONARLINGTON 12, VIRGINIA

UNCLASSIFIED

NOTICE: When government or other drawings, speci-fications or other data are used for any purposeother than in connection with a definitely relatedgovernment procurement operation, the U. S.Government thereby incurs no responsibility, nor anyobligation whatsoever; and the fact that the Govern-ment may have formilated, furnished, or in any waysupplied the said drawings, specifications, or otherdata is not to be regarded by implication or other-wise as in any manner licensing the holder or anyother person or corporation, or con;eying any rightsor permission to manufacture, us or sell anypatented invention that may in any way be relatedthereto.

CV2 N. FTD-215

DATE: 14 September 1962

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FORT WORTH FWP 2376 - 2 53

TEST DATA MEMORANDUMFTDM NO. 2o 1 S

MODEL B-. i ,

TEST NO-- F-8165

TEST: MATERIAL - CHOBERT 3/32 HOLLOW STEEL RIVETS - GALVANIC CORROSION EFFECTSWITH 7075 ALUMINUM - INVESTIGATION OF

OBJECT: To determine the susceptability of the inside surface of Chobert rivets tocorrosion when such rivets are used to attach FXWO20'nutplates to 7075-T6 aluminum alloy.TEST SPECIM-ENS AND PROCEDURE: Two assemblies were fabricated of 7075-T6 aluminum alloyusinp six sets of fasteners for each assembly. The fasteners consisted of FXO1I4-I6*titanium bolts and FXW020-55 aluminum nutplates which were joined to the 7075-T6aluminum with Chobert type 224/310 steel rivets (cadmium plated) as shown in Figure 1.The 7075-T6 alloy was clad on one side, and the assembly was made such that the baresurfaces of the alloy were together (clad sides out). The two assemblies were identicalwith the exception that the rivets on one assembly received a wash prime treatment. Asimilar assembly was fabricated for use as a control. The control assembly containedMS20426-AD3 alumintun rivets instead of the steel rivets.After fabrication, the specimens were exposed to 200 hour salt spray in accordance withFTMSl51, Method 811P Photographs were made at 50 hour intervals. After salt sprayexposure, the bolts and rivets were torqued using inch/paund torque wrench and the failurevalues were recorded.R1ESULTS: Table I lists the torque values required to fail the bolts and rivets after 200hour salt spray exposure. The operating conditions of the salt spray chamber during thetest are given in Table II. Figures 1 thru 4 show specimens after each 50 hour saltspray exposure interval. Figure 5 shows bare aluminum which had been in contact withan aluminum rivet after 200 hours salt spray. Firure 6 is the same except Chobert steelrivets were used.DISCUSSION: Information is needed to determine what effect salt spray exposures haveupon the inside surface of Chobert rivets used to attach FXW 020 nutplates to 7075-T6aluminum alloy.Table I shows that no appreciable difference was found between the torque values ofChobert rivets with wash prime application and the same type rivets with no wash prime.In production these rivets are required to pass 95 - 110 in./lbs. torque without failure,and bolts are required to pass 190 - 210 in./lbs. without failure. All values in TableI are above those limits. Figure 4 shows that after 200 hours salt spray exposure thetwo assemblies (one with wash prime and one with no wash prime) are identical in appear-ance. It may be noted that the assembly with aluminum rivets is comparable to the twoassemblies with Chobert rivets. More corrosion was evident on aluminum which had beenin contact with the Chobert ri'vets than on that which had been in contact with aluminumrivets (see Figures 5 and 6). However, since the aluminum area is so much greater thanthe steel area, corrosion would be minor and the aluminum would soon become passive.CONCLUSIONSt The results of this test show the following:

1. Significant corrosion did not occur in or near Chobert (cadmium plated steel) rivetswhen joined to FXWO2U nutplates and 7075-T6 aluminum alloy and exposed to 200 hoursalt spray.

2. The use of wash prime'on Chobert rivets is not considered necessary in thisapplication.

The tests described in this report were conducted between 8 December 1958 and 9 January1959.*See notes on page 2.WITNESS: 09

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DATE- 30 January 1959 14-OVE W,

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