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1 AD-781 589 CORROSION PROD UCI MORPHOLOGY ONZINC ANODES IN SEA WATER robert Alan Bornholdt INaval Postgradu ate SchoolMonterey, CaliforniaJune 1974 DISTRIBUTED BY:Natioud Trierd SmtiU. S. DEPARTMENT OF COMMERCE5285 Port Royal Road, Springfield Va. 22151 NAVA L POSTGRADUATE SCHOOLM onterey, California00 THESISCORROSION PRODUCT MORPHOLOGY ONZINC ANODES IN SEA Alan BornholdtJune 1974-Thesis Advisor: J. PerkinsApproved for public release; distribution ( crFP\I FSECURITY CLASSIFICATION4 OF THIS PAGE (When Dae Irrnae,. Z~lI 28;'5/ .1,"REPORT DOCUMENTATION PAGE READ INSTPUC:iEOR1. REPORT NUMBER 12. GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMOER4. TITLE (and Sublitle) S. TYPE OF REPORT & PERIOD COVEREDC orrosion Product Morphology on Zinc Master's Thesis;Anodes in Sea Water June 19746 PERFORMING ORG.))

2 REPORT NUMBER7. AUTHOR(s) 6. CONTRACT OR GRANT NUMBER(S)Robert Alan BornholdtS. PERFORMING ORGANIZATION NAME AND ADDRESS SO. PROGRAM ELEMENT. PROJECT. TASKN aval Postgraduate School AREA, WORK UNIT NUMBERSM onterey, california 9394011. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATEN aval Postgraduate School June 1974 Monterey, california 93940 ,s. 'O PAGES14. MONITORING AGENCY NAME & ADDRESS(If different from Controllin Office) IS. SECURITY CLASS. (of this report)Naval Postgraduate School UnclassifiedMonterey, california OECLASSIFICATION'DOWNGRADINGSCHEDULE16. DISTRIBUTION STATEMENT (of thi. Report) IApproved for public release; distribution unlimited.$7. DISTRIBUTION STATEMENT (of tho Abstract etered In Block 20.)

3 II diforent from Report)IS. SUPPLEMENTARY NOTES1S. KIEY WORDS (Continue on reverse old* It necessary and Identily by block number)Corrosion ~.,.,Zinc Anode,- ', ,t20. ABSTRACT (Continue on reveree old* If necessary and identify by block numibor)The corrosion product morphology on a zinc alloy, exposed ina zinc/steel couple in sea water is investigated as a functionof pressure. The results consist of corrosion data obtainedfrom laboratory and ocean cells and data obtained from ascanning electron microscope. The corrosion products areobserved to take two distinct microscopic forms. A porous"sheet" zinc oxide structure is observed on the samples exposedDD ,' 1473 EDITION OF I NOV 6S IS OBSOLETE C.

4 ,3(Page 1) SIR 0to2014 6601 SECURITY CLASSIFICATION OF THIS PAGE (When Del Sn#0#4e#1 CCLU tTY CLASSIFICATION. OF THIS PArf'W'h *(20. ABSTPACT continued)in stagnant sea water. A cloudy, somewhat less porous oxideis observed on the zinc samples exposed in the Form 1473 (BACK)IJan 73 _____SIN 0102-014-6601 sCe^UM'V CL. OkSIFICAION Of THIS PAGEte WhS *flf Enterod)2 Corrosion Product Morphology onZinc Anodes in Sea WaterbyRobert Alan BornholdtLieutenant Commander, United States , United States Merchant Marine Academy, 1961 Submitted in partial fulfillment of therequirements for the degree ofMASTER OF SCIENCE IN MECHANICAL ENGINEERING from theNAVAL POSTGRADUATE SCHOOLJune 1974 Author _ _ _ _ _ _ _ _ _ _-Approved by:_____ _____Thesis AdvisorChairman, Departmeit of Mechanical E-0ineering7 Academic Dear-3 TABLE OF CONTENTSI.

5 INTRODUCTION---------------------------- --------- 12 III. EXPERIMEN~TAL EQUIPMENT AND PROCEDURE------------- 17A. LABORATORY CORROSION CELL TESTS-------------- 17B. LABORATORY PRESSURE CELL TESTS--------------- 18C. OCEAN EXPOSURE ARRAYS----------------------- 19D. SCANNING ELECTRON MICROSCOPE----------------- 20E. POTF:4 TIOSTATIC MEASUREMENTS----------------- 21*F. DIFFRACTION--------------------------- 21G. DATA REDUCTION------------------------------- 22 III. DISCUSCION------------------------------ --------- 23A. LABORATORY CORROSION CELLS------------------ 23B. LABORATORY PRESSURE TESTS------------------- 24C. POTENTIOSTATIC MEASUREMENTS----------------- 25D. X-RAY DIFFRACTION--------------------------- 26E.

6 OCEAN EXPOSURE ARRAYS----------------------- 26F. GENERAL CONCLUSIONS------------------------- 29IV. RECOMMENDATIONS FOR FURTHER WORK----------------- 33 APPENDIX A: THE POTENTIOSTAT-------------------------34 BIBLIOGRAPHY---------------------------- --------------- 35 INITIAL DISTRIBUTION L IST----------- -------------------614 Preceding page blank5 LIST OF ILLUSTRATIONS1. Zinc/Steel Couple W/Nylon Nut and Bolt ---------362. Laboratory Seawater Corrosion Test --------------363. Stainless Steel Pressure Vessel -----------------374. Scanning Electron Microscope --------------------375. Resc arch Potentiostat ---------------------------386. X-Ray Diffractor and Recorder -------------------387.

7 Sartorivs Balance Scale -------------------------398. Zinc Weight Loss. Laboratory, Quiet SeaWater Corrosion Tests ---------------------------409. Clean Zinc (Room Air Oxidation) 610X ----------- 4110. Zinc, 7 Day Quiet Sea Water Exposure, 620X -----4111. Zinc, 14 Day Quiet Sea Water Exposure, 670X -4212. Zinc, 21 Day Quiet Sea Water Exposure, 600X -4213. Zinc, 28 Day Quiet Sea Water Exposure, 600X -4314. Zinc, 21 Day Quiet Sea Water Exposure, 24X -----4315. Zinc, 14 Day Quiet Sea Water Exposure, 620X 4416. Zinc, 21 Day Quiet Sea Water Exposure, 2400X --- 4417. Zinc Weight Loss. Laboratory, Quiet SeaWater Corrosion Tests, 89 psi -------------------4518. Zinc Weight Loss.

8 Laboratory, Quiet Sea Water3 Day Exposures at Various Pressures ------------4619. Zinc, 3 Day Quiet Sea Water ExpQzivk, 89 psi,650X --- ----------------------- 4720. Zinc, 3 Day Quiet Sea Water Exposure, 89 psi,i1Oc ---------------------------------------- -4721. Zinc, 7 Day Quiet Sea Water Exposure, 89 psi,22X ---------------------------------------- ----148622. Zinc, 7 Day Quiet Sea Water Exposure, 89 psi,575X ---------------------------------------- ------4823. Zinc, 7 Day Quiet Sea Water Exposure, 89 psi,2300X ---------------------------------------- ---- 4924. Weight of Zinc Oxide at Various EquivalentDepths (3 Day Exposure) --------------------------5025 Anodic Polarization Curve of Zinc inQuiet Sea Water -----------------------------------5126.

9 Zinc, Anodic Polarization, 5 min. at 10ma, , 2500X --------------------------------------52 27. Zinc, Anodic Polarization, 5 min. at 100ma,-C9v , 2300X 528. Zinc, Anodic Polarization, 5 min. at 1000ma, , 2400X --------------------------------------53 29. Zinc, Anodic and Cathodic Polarization Cycle,2400X ---------------------------------------- -----5330. Zinc, Anodic Polarization, 5 min. at 100ma, , 575X, "Charging Effect ObservedDuring SEM Study" --------------------------------5431. Zinc Weight Loss. Ocean, 3 Day Corrosion Tests 55-2. Zinc Weight Loss. Ocean, 9 Day Corrosion Tests 5633. Zinc, 1 Day, 50 Foot Ocean Exposure, 25X ---------5734. Zinc, 1 Day, 50 Foot Ocean Exposure, 630X ---------5735.

10 Zinc, 9 Day, 50 Foot Ocean Exposure, 24X ---------5836. Zinc, 9 Day, 50 Foot Ocean Exposure, 600X"Cloudy Oxide Structure" --------------------------- 5837. Zinc, 9 Day, 50 Foot Ocean Exposure, 2400X"Cloudy, Apparently Continuous Coherent Coating" - 5938. Zinc, 9 Day, 100 Foot Ocean Exposure, 24X --------5939. Zinc, 9 Day, 100 Foot Ocean Exposure, 600X"Cracked Coherent Coating" -----------------------6040. Zinc, 9 Day, 10) Foot Ocean Exposuire. 2400X ------6041. Zinc, 9 Day, 150 Foot Ocean Exposure, 20X --------61742. Zinc, 9 Day, 150 Foot Ocean Exposure, 600X ------6143. Zinc, 9 Day, 150 Foot Ocean Exposure, 240OX 6244. Zinc, 9 Day, 100 Foot Ocean Exposure,"Macroscopic Deterioration" ---------------------6245.