TO - Defense Technical Information Center

1 UNCLASSIFIEDAD NUMBERAD466284 NEW LIMITATION CHANGETOA pproved for public release, distributionunlimitedFROMD istribution authorized to Gov' and their contractors;Administrative/Operational Use; 10 MAY1965. Other requests shall be referred toDepartment of the Air Force, Attn: PublicAffairs Office, Washington, DC ltr, 7 May 1970 THIS PAGE IS UNCLASSIFIEDma 30, 1965C -DCCORROSO orASlfOMAINC,~%ovMMus OhiAL 4Y THYENNOTICE: 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. thereby incurs no r-sponsibility, nor anyobligation hatsoever; and the fact that the Govern-ment may have formulated.

2 Furnished, or in any waysupplied the said drawings, specifications, o. otherdata is not to be regarded by implication or other-wise as in any manner licensing the holder or anyother person or corporation, or conveying any rightsor permission to manufacture, use or sell anypatented invention that may in any way be , Information Center was e -ablished at Battelle NMnil. bls*tt4thic requaa-t of the Office of the Director of Defense Research :kAn Engineering-to pr widv Gavvr .xnent contractors and their suppliers tech!'ical assistance and inform stion on titanium, btrVyUU %magnesium, aluminum, refractory metals, high-strength alloys for high-temnpe*'atutrer klicorrosion- and oxidation-resistant coatings, and thermal-protection systems.

3 Its fuaittia., jthe direction of the r~'ice of the Director of Defense Research and Engineering, are 4s flo1. To collect, store, and disemiirate techaical Information on the currentstatus of research and development of the above To supplement estaolished Service activities in providing Technical ad-visorv services to producers, melter., and fabricators of the , and to designers and fabricators of military equ~ipme~nt Con-taining these To assist the Go',ernment agencies and their contractors in developingtechnical data required for preparation of specifications for the On assignment, to conduct surveys, or laboratory research investiga-tions, mainly of a short-range nature, as required, to ascertain caoftesof troubles encountered by fabricators,, or to fill minor gaps in estab-lished research No.

4 AF (615)-l112 7 Project No. 8975 Roger J. RunekDirectorANoticesWhe rro _--rict drawings, specificfats, or otker 4&,&a are used toanthau in cona. dos with a definitely related Coernrnenj aprtioa jhGoverumenu..er*by iv4, ;a .%o responsibility nor any obtz;*tion What*"oer; k4d W:"ftJ0"IGovernnt May have formulated, furnished, or in aily waiy suopled- the sa1id a4 Stiono, or othtr data, is not to be rega~rdod by implication or othaerwise a~s la x.' hol~ez or aUY Other Person or corporation, .or convOylag AV rightt or Poraissif toture, use., or, a0e1i aY !Wtek"d iAVention thtt WAY in any Way be relatea a~ stetrs may obWAn coplo g of thi report from the r (D=C), Ca&MOron Statiou , Dtftt 5.

5 , 5010 Duke Street, lzzla ~~n,&S1~411tijd of tWe report is 1it~d because tho report net tochnoleg i4."I~&I~latho stateic: embargo Lists "X Wedd ibml export or re'epr 5Of 19~49 (63 STAT. Thas *aj~uWd. ('50 UV & C. APP. , a. s taC4000 of thi. roe"r should nt be rvtu=*d tW the tkMgrWrgk~Pttw -eAir ftrc* Base, 0 Oiuls rtur' is .bvy .ctriq ccaIntractaI abucinat or bot*o 04 a spnikl Report 216 May 10, 1965 CORROSION OF MATERIALS BY ETHYLENE GLYCOL-WATERbyJ. D. Jackson, P. D. Miller, F. W. Fink. and W. K. BoydtoOFFICE OF THE DIRECTOR OF DEFENSERESEARCH AND ENGINEERINGDEFENSE METALS Information CENTERB attelle Memorial InstituteColumbus, Ohio 43201 TABLE OF CONTENTSSUMMARY AND DISCUSSION.))

6 INTRODUCTION ..PHYSICAL AND CHEMICAL PROPERTIES ..vecomposition of Glycol ..CORROSION BY ETHYLENE GLYCOL .. 2 Uninhibited Ethylene Glycol .. 3 Time Dependence .. 3 Effect of pH .. 3 Effect qf Conceptration .. 3 Effect of Temperature .. 3 Effect of Aeration .. 3 Effect of Chloride Ion .. 3 Galvanic Corrosion .. 3 Effect of Velocity .. 5 Effect of Heat Transfer .. 5 Inhibited Ethylene Glycol .. 5 Commercial Inhibitors .. 5 Borax-Base Inhibitor .. 6 Sodium Bensoate-Sodiuxn Nitrite Inhibitor .. 6 Triethanolxmine Phosphate/Sodium Me rcaptobensothiasole System ..10 Soluble Oil .. 11 Chromate Inhibitor ..11 Miscellaneous Inhibitors.

7 12 Depletion of Corrosion Inhibitors .. 13 REFERENCES .. 14 APPENDIX A. TEST PROCEDURES USED IN ETHYLENE GLYCOL STUDIES o. A-iCORROSION OF MATERIALS BY ETHYLENE GLYCOL-WATERJ. D. Jackson, P. D. Miller, F. W. Fink, and W. K. Boyd*SUMMARYS olutions of ethylene glycol are being con- Galvanic attack can occur in glycol solutions,sidered as heat-transfer media for radiators in increasing the attack of the less resistant of twomanned space capsules. Most available corrosion coupled metals. Steel is the least resistantdata, however, are based on automotive and diesel followed by cast iron, aluminum, solder, brass,engine coolant systems, and copper.

8 Pitting can sometimes occur onaluminum when coupled to other the presence of oxygen, solutions ofethylene glycol at elevated temperatures tend to No velocity effects were found for a claddecompose into glycolic and formic acids. The aluminum alloy up to a velocity of 3000 ft perpresence of such decomposition products tends to minute. Under conditions of heat transfer, theincrease the corrosion rates of most metals in corrosion rate of cast iron solutions. It is, therefore, recommendedthat ethylene glycol systems be designed as With the addition of suitable inhibitors toclosed nonaerated systems, glycol solutions, the corrosion rates of mostmetals can be reduced to a negligible space applications, the lighter metals Some inhibitors, however, are specific to certainsuch as aluminum, magnesium, beryllium, or metals and will increase the attack on others.

9 Intitanium would be candidate materials of con- addition, ions from one metal can increase thestruction. Of these metals, titanium would be corrosion of another even though the two are notexpected to be highly resistant. Corrosion rates in direct contact. Thus, in cooling systemsof aluminum in uninhibited solutions would be of where several different metals are present, athe order of 1-2 mpy, while magnesium probably combination of compatible inhibitors is often re-would have low corrosion rates only with an quired for adequate added. Rates of attack for berylliumwould be somewhere between those for aluminum Among the most common corrosion inhibi-and magnesium.

10 Tors which have found successful use in ethyleneglycol solutions are:Heavy metal ions such as copper would beexpected to increase attack and cause pitting of (1) Borax, usually with additivesaluminum, beryllium, and magnesium unlessadequately inhibited. The light metals should notbe coupled to dissimilar metals in ethylene glycol (3) Triethanolamine phosphate (TEAP)-solutions, sodium me rcaptobenzothiasole (MBT).In uninhibited glycol solutions, the corrosion A number of patented inhibitors, based on borax,rates of all metals studied were found to be con- are with time or to decrease. When the glycolsolution was continuously renewed, the corrosion An inhibitor system used by the U.