AD-AD7 3 190 NAVAL AIR DEVELOPMENT CENTER WARMINSTER PA AIRCRAFT -ETC F/A 11/2SALT SPRAY TESTING OF METALLIC -CERAMIC COATINGS U)FEB 80 E J JANKOASK

UNCLASSIFIED NAOC-79257-60mhhhmhh

(lii 1. L281 125

1111(1L25 jffl.4L * .

CRHOCOPY RLSOLUIION ICYI (iARINAIJONAI BU All 01 IANlI k 1'4, A

REPORT NO. NADC-79257-60 LEVEL

SALT SPRAY TESTING OF-HETALLIC - CERAMC COATINGS

V .,

E. J. JankowskyAircraft and Crew Systems Technology Directorate

NAVAL AIR DEVELOPHMT CENTER:;* Warainster, Pennsylvania 18974

* "8 February 1980

PHASE REPORTAIRTASK NO. A510-5102/001-D/9W0625-O000

F-18 Materials Technology Support

ORICINAL CONTAINS COLOR PLATESs ALL DMREPRODUCTIOM WILL BE IN BLACK AND WtrE

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

I'!:; i .... D T ICPrprdfor D-ra%

NAVA AIRSYST EMS CO NM P N ,- - -.

Department of the Navy APR 2 11980Washingon, D.C. 20361

"1 ' I =IS DOUMT IS 13EST QUA ITY ?PMCTICABLII.

TOi COPY nUI ISHED TO DDC CI'TTAIND A.ITQUIFICAM WJVBE~T OF PAGES WU0H DO 0 0.IROD LEGIBLY.

-S

II

NOTICES

REPORT NUMBERING SYSTEM - The numbering of technical project reports issued by the Naval Air DevelopmentCenter is arranged for specific identification purposes. Each number consists of the Center aconym, the calendaryear in which the number was assigned, the sequence number of the report within the specific calender year, andthe official 2-digit correspondence code of the Command Office or the Functional Directorate responsible for thereport. For example: Report No. NADC78015-20 indicates the fifteeth Center report for the year 1978, and prepared (by the Systems Directorate. The numerical codes are as follows:

CODE OFFICE OR DIRECTORATE

00 Commander, Naval Air Development Center01 Technical Director, Naval Air Development Center02 Comptroler10 Directorate Command Projectsr" p 20 Systems Directorate

L 30 Sensors E Avionics Technology Directorate40 Communication & Navigation Technology Directorate50 Software Computer Directorate60 Aircraft & Crew Systems Technology Directorate70 Planning Assessment Resourcesso Engineeing Support Group

PRODUCT ENDORSEMENT- The discussion or instructions concerning commercial products herein do not constitutean endorsement by the Government nor do they convey or Imply the lerm or right t use such products.

APPROVED BY: DATE:_________

E. 3. S

DISCLAIMER NTC

THIS DOCUMENT IS BEST QUALITYPRACTICABLE. THE COPY FURNISHEDTO DTIC CONTAINED A SIGNIFICANTNUMBER OF PAGES WHICH DO NOTREPRODUCE LEGIBLY.

SECURITY CLASSIFICATIO14 OF THIS PAGIE (When Dees Entered) _________________

4 ~AT PR J ESTING OF METALLIC - 1Phase/epwXERAMC COAtINGS -- Fr *M61

E. Jankowk

Aircraft & Crew Systems Technology Directorate5

11. CONTROLLING OFFICe NAME AND ADDRESS

Department of the Navy

UNCLASSIFIEDo~w I AL DECLASSIFICATION, DOWNGRADING

SCH4EDULE

W0 DISTRIBUTION STATZMENTNI thag cm

Approved for Public Release; Distribution Unlimited~.

I Acceseion For17. DISTRIBUTION STA19MIENT (of the abstract entered in Block 20, it different fo Repor) NTIS G:ZikI

DDC TABUnann~u.:ed

IS. SUPPLEMENTARtY NOtES B

19. KEY WORDS (Centinue en ,.vorse did* it necessay end idonfr&& b lack number) I al01

Metallic-ceramic coatings itCorrosion testing

20. A b&AACT (Centlue en *posse elde if neeeeefh and Idontit' by bleck nmer~)

* * Fifteen metallic-ceramic coatings consisting of aluminum or aluminum-* I magnesium pigment suspended in an inorganic binder were applied to steel

panels and tested for corrosion resistance in S02 -salt fog and 5% salt fog,respectively. Four coatings offered better protection than the MIL-C-81751coating (Sermetel W). The best coating was Sermetel 762. Sermetel 763,Sermetel 725, and a dual coating of Sermetel W, Class 4 over Class 2,followed in order of decreasing protection.A

DO I AI. 1473 ED1-OOION OP NOV635 IS O tflOSSIFIES/N 0 102- LPOI04- 6601 SICURIlY CL.AIFICAION *It THIS PAGIL (Whom Date E 7 iJlJe*

NADC-79257-60

SUMMARY

INTRODUCTION

This investigation was conducted under reference (a) for the purpose of deter-mining the corrosion resistance of several new Sermetel coatings that might beuseful for protecting steel aircraft components.

Sermetel W is a metallic-ceramic type coating containing aluminum powder in aninorganic, chromate-phosphate binder. It meets the requirements of MIL-C-81751and has been used successfully for many years for the corrosion protection ofvarious components in naval aircraft.

The new coatings are based on the same concept of metallic pigment suspended inan inorganic binder material. All the coatings tested in this investigationcontained either all aluminum pigments or combinations of aluminum and aluminum-magnesium alloy. In some cases, an overcoating of a chromate inhibited sealercoating (Sermetel 570A) was used to improve corrosion resistance. The coatingswere applied by spraying followed by curing at temperatures ranging from 2040C(4000F) to 5660C (10500F).

Fifteen coatings were evaluated for protective value on steel in both 5% salt

fog and S02 salt fog.

StIM14ARY OF RESULTS

Results of corrosion tests indicate that the best Sermetel Wf coating isClass 4 which is cured at 3430C (6500F) for 1/2 hour followed by burnishingwith glass beads. Class 2 was next and Class 1 was a poor third. Four of thenew coatings offered better protection than Sermetel W, Class 4. In order ofdecreasing protection, they were: Sermetel 762, Sermetel 763, Sermetel 725,and a dual coating of Sermetel W, Class 4 over Class 2. The remaining coatingswere all equal to or poorer than W, Class 4.

Several coatings survived the 1056 hour 5Z salt fog exposure test, but allexcept one panel of one coating failed within 456 hours of SO2 - salt fogtesting.

CONCLUSIONS

Sermetel 762 and 763 are the best of the coatings tested for the protection ofsteel against corrosion.

Sermetel 725 is the best low temperature cure coating (343 0 C).

Class 4 (glass bead burnished) is the most corrosion resistant of the MIL-C-81751classes.

The lowest curing temperature (2040C) results in coatings with the poorestcorrosion resistance.

Sermetel 735 was the better of the two thin coatings (20 mm) tested.

/.-

INADC-79257--60

RECOIMNDATIONS

1. It is recomended that consideration be given to the use of Sermetel 763,762, and 725 for the protection of steel components against corrosion wheretempering temperatures are higher than the required curing temperatures.

2. It is recommended that testing of the best systems be extended to determinewhether they meet all the requirements of NIL-C-81751.

ii.I

ADC-79257-60

TABLE OF CONTENTS

Page

Introduction . . ... . . . . . . . . . . . . . . . .... . .

Summary of Results . . . . . . . . . . . . . . . . . . . . . i

Conclusions. ........ . . . . . ............ j

Recommendations ................. . . . . . ...... ii

* LIST OF TABLES. . . . . . . . . . . . . . . . . . . . IV

LIST OF FIGURES . . . ... .. . . . . . . . . . ........ iv

BACKGROUND. . . . . o . . . . . . . . . . . . . . . . . .. . 1•TEST METHODS . . .o.. . .. .. .. .. .. .. .. . ..... 1

Specimenspa . . . . . . . . . . . . . . . . . . . . . . . *.. 1

5Z Salt Spray ......................... 3

S02-Salt Spray Te.. . . . . . . . . . . . . . . . . . . . . 3

RESULTSC. . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Z Salt Spray Tet ..... ...... ........ 3

SO2-Salt Spray Tests. .......... . .. ...... 4

iCONCLUSIONS *.. .. .. .. .. ....... .. . .... 4

REFERENCES. - @ . .. 4

IW

NADC-79257-60

LIST OF TABLES

Table Title Page

I List of Specimens. . . . . . . . . . . . . . . . . . . .. 2

II Sermetel Coatings on 1020 Steel, Exposure TestResults o.. .. .. .. .. . .. ... 5

LIST OF FIGURES

Figure Title page

1 Salt Spray Exposure Failure Times - SermetelCoatings . .. .. .. .. .. .0. .. .. .. .. ... 6

2 Appearance of Sermetel Coatings at Failure -51 Salt Spray . . . . ... . . . . . . . ...... 7

3 Appearance of Sermetel Coatings at Failure -5% Salt Spray . . . . . . . . . . . . . . . . . . . . . 8

4 Appearance of Sermetel Coatings at Failure -5Z Salt Spray . . . . . . . . . . . . . . . . ... .

5 Appearance of Sermetel Coatings at Failure -5Z Salt Spray . . . . . . . . . . . . . . . . .. . . . 10

6 Appearance of Sermetel Coatings at Failure -s S2 Salt Spray. . . . . . . . . . . . . . . . . . . . . 11

7 Appearance of Sermetel Coatings at Failure -SO2 Salt Spray. . . . . . . . . . . . . . . . . . . . . 12

8 Appearance of Sermetel Coatings at Failure -

so2 Salt Spray . .. ............. . . .. 13

9 Appearance of Sermetel Coatings at Failure -

so 2 Salt Spray. .................... 14

IS

iv. . v

V. -.-

I

NADC-79257-60

BACKGROUND

Cadmium has been used extensively for the protection of steel aircraft partsagainst corrosion. Recently, the Environmental Protection Agency hasrequested the Department of Defense to eliminate cadmium from any applica-tion for which an alternate coating can be used. It was felt that some ofthe new Sermetel coatings might be used in some applications. Their greatestshortcoming, as far as general use is concerned, is the high curing tempera-ture required. It was for this reason that lower curing temperatures forlonger times were tried with some of the coatings. Additionally, Teleflex,Inc., manufacturer of the Sermetel coatings, has conducted a great deal ofresearch work to improve their basic Sermetel W process. Among theseimprovements is a clear, corrosion inhibited sealer coat applied over thealuminum pigmented coat. Modifications have also been made in the pigmentsystems.

q

One application directly related to the F-18 is the inside of the landinggear. Ion vapor deposited aluminum is difficult to coat in this area andcadmium plating poses some danger of hydrogen embrittlement. If the curingtemperature could be kept below 3020C (5750F), the tempering temperature ofthe 300 M steel in the landing gear, then one of the Sermetel coatings couldbe used. In other areas, where the tempering temperature is higher, some ofthe other Sermetels might serve.

This investigation was undertaken at the request of the Naval Air SystemsCommand (AIR-5163C2).

It should be noted that no attempt was made to determine the elevated

temperature properties of the coatings.

TEST METHODS

SPECIMENS

Specimens consisted of 5 x 10.2 x 0.32 cm (2" x 4" x 1/8") panels of AISI1020 steel coated with the various systems by the Sermetel Division ofTeleflex, Inc. Coating systems are listed in Table I. All the coatingsexcept 622 are aluminum filled chromate/phosphate dispersions in a water base.Sermetel 622 is an aluminum and aluminum magnesium filled chromate/phosphatedispersion. All are sacrificial to steel (provide galvanic protection) exceptSermetel W, Class 1 which acts only as a barrier against the corrosiveenvironment. SermaSeal 570A is a chromate-based topcoat sealer without anypigment.

I1

A,..

,.. . . . -.... .. . . . . . . . . . . . . . . . .

NADC-79257-60

co an V-1 &Man an in In Go co c aN a co en C" 0A A.. *4 A *4 14 . 4

"..M A l en C C" cn C" 0 0n 0 l l Cl s'

'54 % 0 4 N % D I-

4* MV. CO *.. O i

ma 0 0i q2 an 1 00

A 0 A. 4uw4 w. w4 V i w ul .4 40 0 0 0 01

41 Al A Inla 0 C C4 % 544593 C". C4 - "- In Cl ai C Clo w w4 %a4 60. %0 u@O' 0

a. v C4 a + 448 O.-4 6 0 w IV 0.4 V to1 54 U 11 0 a 054 a.- 00

*404 ci ce 0 A0 a .*. ". * 0 '.55 0 10 -A 4. 4 '4 CO 'M4 UU (A6 4 oO

U) r4 I ~ 0 '4*. - n -A ~ 40 *'* ~ cicic %a *0 U@ 0cc 54

04 004 14 0 0 0 4 0 0dw0 .Cw 0O. m w6 ~ U 5

0 0

04 I C-4 4 Cl 4 4 C4 r4 r P

0)E 0 in 0 0 no%I %a 4 4c :4 ;; r4I arG DG0. %0 0 0 *

an 0 n 0 0 0 n 0o 0 106 0'..

a- U ~ n 0 o a o SO a c 0 0 0 0 a0

00

0

UU -I v-I C4 C4,.4

u0 U Ut Ul P. Go &M@ an N%0 a ~ -an a cs -4 &M Cl %C 'o 'C C

04 mt OR I- r % 1%% P% 1% f% '

a 0 0 o 0 a 0 0 a 0 0 0 0 0 041A54 41 41 41 41 415 &a 41 8 41 4

r4 "1 04 fn e% a - n -4 -e fIn i % a( 4% r% @%

0u r -4 4" C in 's &M .ci .e- Pan an C '

cl

2

NADC-79257-60

5% SALT SPRAY

Half of the panels were exposed to 5% salt fog in 15 degree racks in accordancewith ASTM B-117. All panels were scribed with an X through the coating priorto exposure. Panels were examined every day for signs of rust in the scribes.Testing was discontinued after 1056 hours.

S02-SALT SPRAY

The remaining panels were scribed and exposed to S02-salt spray in 15 degreeracks. In this test, sulfur dioxide gas is introduced into the 5% salt fogbox for one hour four times every 24 hours. Reference (b) gives a detaileddescription. The test is much more severe than the standard salt fog testand is considered to simulate a carrier deck environment more closely. Thepanels in S02-salt spray were also examined daily for signs of rust in thescribes. The first sign of rust was considered failure. The first panel tofail in the series was used for failure times given in the results section.

RE S ULTS

5Z SALT SPRAY TESTS

Results of salt spray tests are given in Table II and shown in Figures 1 throughthrough 5. Although the first rust in any of the scribes was taken as thefailure time for the series, there was considerable difference in the overall

appearance of the panels at failure. It is for this reason that Figures 2to 5 were taken. It is obvious from the photographs that some of the systemsfailed only in the scribes, while others showed general corrosion on the panelfaces as well. Testing was discontinued after 1056 hours of exposure. Thefollowing coatings showed no rust in the scribes at the end of the test:

W Class 2, 5660C - 1/2 hour cureW Class 4, 3430C - 1/2 hour cure

* W Class 2 and W Class 4, 5660C - 1/2 hour cure735, 3430C - 1/2 hour cure758, 2040C - 1/2 hour cure763, 5660C - 1/2 hour cure761, 2040C - 1/2 hour cure762, 4270C - 1/2 hour, 3430C - 1/2 hour cure622, 4270C - 1/2 hour cure

Two of the coatings, 754 and 761, had considerable rust on their faces at theend of the test. The 754 coating failed in the scribes in 120 hours, but the761 coating was unusual in that there was no rust in the scribes at the end ofthe 1056 hour test period, only rust on the faces. The 758 coating had rustonly on the edge of one scribe, but considerable white corrosion over all thepanels at 1056 hours. The 725 coating had excellent overall appearance. A fewtiny rust spots appeared in the scribes of one panel after 1056 hours, other-wise this coating would have been among those passing. In overall appearance,it was better than 735.

1* 3

NADC-79257-60

S02 -SALT SPRAY TESTS

Results of S02-salt spray tests are given in Table II and shown in Figures 1and 6 to 9. None of the coating systems tested withstood more than 456 hoursof testing without rusting in the scribes. All of the coatings showed signsof rusting on their faces at the time they failed in the scribes, except thosethat failed in the scribes after very short exposure. Coating 754 blisteredin 24 hours. The best coatings in this test were 762 and 763, both failingafter 456 hours. 725 was next with failure time of 360 hours. Of the twothin coatings tested, 717 and 735, 735 was the better.

CONCLUSIONS

Sermetel 762 and 763 are the best of the coatings tested for the protectionof steel against corrosion.

Sermetel 725 is the best low temperature cure coating (3431C).

Class 4 (glass bead burnished) is the most corrosion resistant of theMIL-C-81751 classes.

Sermetel 735 is the better of the two thin (20 n) coatings tested.

Low temperature (2040C) cures generally result in coatings that offer poorerprotection than higher temperature cures.

S02-Salt spray is much more corrosive to coatings of the Sermetel type thanstandard 5% salt spray.

REFERENCES

(a) AIRTASK No. A510-5102/OOl-D/9W0625-O000, F-18 Materials TechnologySupport of 9 Nov 1978

(b) Naval Air Development Center Report No. NADC-77252-30, AcceleratedLaboratory Corrosion Test for Materials and Finishes used in NavalAircraft, 14 Sep 1977

4

NADC-79257-60

TABLE II.* SERMETEL COATINGS ON 1020 STEEL, EXPOSURE TEST RESULTS

Time to Time toCoating Cure Temperature Failure (hours)- Failure (hours)-

Identification and Time S02 Salt Spray * 5Z Salt Spray*

W, Class 1 2040C - 24 hours 24 24

W, Class 1 3430C - 1/2 hour 24 24

W, Class 2 5660C - 1/2 hour 120 1056 *

754 2040C - 2 hours 24 120

W, Class 4 3430C - 1/2 hour 192 1056 *

W, Class 2

&W, Class 4 5660C - 1/2 hour 216 1056 *

759 2040C - 2 hours 24 24

735 3430C - 1/2 hour 192 1056 *

717 5660C - 1/2 hour 96 120

758 2040C - 2 hours 24 1056

725 3430C - 1/2 hour 360 1056

763 5660C - 1/2 hour 456 1056 *

-761 2040C - 2 hours 96 1056 *

*762 4270C - 1/2 hour 456 1056 *

3430C - 1/2 hour

622 4270C - 1/2 hour 96 1056 *

*First failure of the panel series.First sign of rust in the scribe marks.

**Did not fail -tests discontinued.

NADC-79257-60

NN-"~ 9 ; d

a _________________________________________

_______ _______________________ .4 ~A.4.

I! __________________________________

.4 0 ~.4

~ .4 .4 - S

* d ~1 U)* .4 *.@ ________________________________ C,

_______________________________ a0 0 ~ - .4 9.4

- q ___________ 8= ______________________________________ U N

4

= U 4.. 4 .4 U)

E.G

4 - ~ 3

II 3i~; :g U)

___________________ 9 U..* a

______________________________ a

3 ~ 3 3 5-4

3 be

ISea ~

a

0 * P 3iI 1:1311*6 .4 .4 -UUU~ AIiM MA tim

/"~5S A ~i I6

-4.

NADC .79 257 .60

a06

o .

60

60

40ul

U)

C4 4

-dIL

FIGURE

- * m7

uJ mu-

NADC-79257-60

0 S

404V V

a.

V 0I

4CI'.

4 FIGURE -

NADC-79257-60

0

00

N 0~

000

0 - U'

r4

FIGRE.

NADC-79257-60

C14

00

*z

94 AU a0* a-'VI 0 I

sa'U. zA4

10

r---

NADC-79257-60

Mda

0 0VI

nv

3tb

U ma

00

z

room4

NADC-79257-60

V V U

vaV .

010U-Re9

4 gv,

0 oN

V V

IL

FIGRE4

124

T",r4 I-

NADC-79257 -60

4pA

o 0

oo

o;U N C4

osC -&

13 FIUE 4

NADC-79257.60

lu

v

C4

44

cl;lC4 0

Ia

0

V IA0 o0

N4 <

Clau

FIUR14

NADC-79257-60

D IS TR IB U TIO0N L IS T

t AIRTASK NO. A510-5102/O0l-D/9W0625-OOF-l8 Materials Technology Support

No. of Copies

NAVAIR (AIR-950D) . . . . . . . . . . . . . . . . . o o 32 for retention 81 for AIR-5163D1

1NAVAIREWORKAC, Alameda (Code 340). .......... .. .. .

Jacksonville (Code 340) . . . . . . . . 0 0 . 6Norfolk(Cod3. . .. . . .. . . . .. . 1North Island (Code 340).. ...... ..... IPensacola (Code0) . . . . .. ..... o A

MCAS, Cherry Point (Code 340). o o........ . . . 1

I. F-18 Materials and Processes, McDonnell Douglas Aircraft Co.,Box 516, St. Louis, Missouri 63166 . . . . . ........ .o 1

Sermetel Incorporated, Limerick Road, Limerick, Pennsylvania 19468Attention: Mr. Allen Matz . . . . . . . . . . . . ...... . o

DT Co 6 oo 0 61