Albrecht, R. H.

Jensen, D. P.

Schnake, P.

English

NASA Technical Reports Server

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I 
NASA CONT-3ACT IUS 8-11788 
FINAL REPORT 
(June 26, 1964 through November 30, 1964) 
Procurement Requests No 1-4=30-01070 
No 1-4-30-01070 S1 (ll?) 
I 
. 
DEVELOPM9NP OF CORROSION 
INHIBITING VHITE PRINGR 
ITHRUI ! N65-124 19 IACSESSION NUMBER) 3 f e 
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tNASA CR OR TMX O R  AD NUMBER) ICATEGORY) 
Paul Schnake 
Derwood P . Jens en 
Robert H. Albrecht 
Chicago Lac n uer Laboratory 
Prepared f o r  : 
GEORGE C. NARSHALL SPACE FLIGHT CENTm 
NASA 
HUNTSVILLE, ALABAMA 
GPO PRICE $ 
OTS PRICE(S) $ 
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Page 2 
ABSTRACT 
Studies were conducted t o  develop a corrosion r e s i s t i n g  
white primer. 
pigments and vehicles  were evaluated. 
flower RJlOO urethane varnish was found to contr ibute  superior 
corrosion resis tance,  l a rge ly  without deleter ious e f f e c t s  on 
other  film propert ies ,  A combination of Titanium =oxide and 
Zinc Molybdate pigments was found t o  contr ibute  t o  a maximum i n  
hiding and corrosion resistance,  
In  the  development of t'lis primer the e f f e c t s  of 
A vehicle  based on a saf- 
Various cleaning and metal treatment methods as well 
as various film thicknesses of the  primer were evaluated t o  achieve w maximum metal protect ion at a minim-& p r i m r  weight, 
INTRODUCTION 
THE GOAL 
I. To determine the extent to  which 2219 Aluminum Alloy is 
effected by salt  spray corrosion. 
11. To determin3 an e f f i c i en t  method of metal pretreatment. 
111, To develop a primer or  priming system which has the  f o l -  
lowing properties : 
A. The primer is  t o  be white, low i n  density, and have 
appreciable coverage, 
"h i t e  Flat  Vnamel are t o  form a system of mi-nimum 
weight which would be achieved only by the use of a 
white primer (a  colored primer wou ld  reauire  in- 
creased film tblickness of topcoat to  achieve desired 
covarage and whiteness). 
The primer plus IIIL-E-s5s6A 
B. The primer mus t  contribute t o  the  corrosion inh ib i t ion  
of the system as determined by two salt spray tests. 
1. 
2, 
1 Two weeks i n  f ive  per cent salt spray 
Two weeks i n  twenty per cent salt spray 1 
C, The primer is t o  m e e t  the  physical requirements, 
film and resis tance properties, and qual i ty  pro- 
visions of MILP-8585A. 
THE SCOPE OF WORK 
I, An evaluation of various cleaning methods f o r  adhesion pro- 
motion and corrosion inhibi t ion leading t o  an improvement 
of corrosion resis tance,  
11. An evaluation of various vehicles, pigments and i n e r t  pig- 
ments t o  a r r ive  a t  good s t a r t i n g  formulations. 
111. An evaluation of wash primers f o r  possible system advantage - 
f i lm  thickness var ia t ion of  each primer. 
IV, An evaluation of additivss and formulation refinement, 
'Vhite primer, E42 V 2, developed t o  meet the per- 
formance of MIL-P-858SA was tes ted and found t o  be def ic ien t  
i n  drying rate, but acceptable f o r  protect ive quali t ies.  
An evaluation of corrosion resis tance of 2219 Aluminum 
Alloy was conducted. This showed t h a t  metal pretreatment s,zemed 
t o  have l i t t l e  e f f ec t  on the  corrosion resis tance of t h i s  alloy. 
An evaluation of vehicles, pigments and i n e r t s  was con- 
ducted. The results of t h i s  evaluation showed t h a t  the ni t ro-  
c e l l u l o s e c a s t o r  maleic ros in  varnish, the vinyl-epoxy and the 
safflower RJlOO urethane varnish were the most probable vehicles 
t o  y ie ld  sa t i s fac tory  resul ts .  The pigment combination should 
be about eizhty per cent t i t an ium dioxide and twenty per cent  
zinc molybdate. 
enough t o  justify t h e i r   US^. 
I n e r t  pigments d i d  not appear t o  contribut? 
An evaluation of cleaning methods, film thickness, 
Proper cleaning seemed wash primers and primers w a s  conducted. 
t o  give eaually sa t i s fac tory  r e su l t s  t o  t h a t  of wash primers, 
A sui table  f i l m  thickness seemed t o  be 5/10 mil. 
cel lulose - castor  maleic rosin varnish vehicle  was eliminated 
from t e s t i n g  due t o  f a i l u r e  i n  several  areas. 
The ni t ro-  
An evaluation of formulation refinements was conducted. 
The optimum pigment by volwne concentration was found t o  be about 
45% and the  so l id s  content should be about 5%. 
S a l t  spra.y tests extended t o  s ix  weeks of these las t  
two evaluations did not show appreciably more f a i l u r e  than did 
the two week tests. 
An evaluation of goal fu l f i l lment  indicated t h a t  we 
d id  f u l f i l l  our  objective. 
1. These tests were extended t o  include six weeks o r  lo00 hours 
i n  sa l t  spray. 
2, An evaluation of goal fulf i l lment  including six weeks o r  
1000 hours i n  salt spray was added per supplemental agrsa- 
ment modification number 1. 
Page 5 
RESULTS ANTI DISCUSSION 
I n  t h e  development of t h i s  primer the  e f f e c t s  of 
pigments and vehicles were evaluated. 
safflower R J l O O  urethane varnish was found t o  contr ibute  
superior corrosion r e s i s t ame ,  l a rge ly  without deleter ious 
e f f e c t s  on other  film proqerties. Various vehicles  were 
evaluated including those used i n  NIL-P-6889A and. MIL-P- 
8585A, but  none were equal i n  e i t h e r  corrosion protact ion 
and film propert ies  t o  the safflotrer R J l O O  urethane varnish. 
Although the  vinyl-epoxy vehicle was nearly eaual  t o  it, 
time limited thewgcessary s t a b i l i t y  information f o r  se r ious  
consideration of t h i s  vehicle. 
A vehicle  based on a 
A combination of Titanium Dioxide and Zinc ilolyb- 
date pigments was found t o  contribute towards a maximum i n  
hiding and corrosion resistance. 
age requirement of t h i s  primer and i n  an a t txnpt  t o  achieve 
maximum corrosion res i s tance  the optimum pigment combina- 
t i o n  w a s  found t o  be 90% Titanium qioxide and 10% Zinc 
Holybdate. Although a pigment by volume concentration of 
45% was found t o  be opt imq,  40% was used t o  give b e t t e r  
f i lm  strength and a more continuous film a t  minimum thick- 
neSS2S. 
Because of t he  high cover- 
The r e su l t an t  formulation w i l l  provide maximum 
protect ion t o  2219 Aluminum Alloy with a minimum wipht. 
I n  the evaluation of goal fulf i l lment ,  no s ign i f i can t  dif- 
ference between primers was found during s i x  weeks of s&lt 
spray tes t ing ,  (See Data if1 f o r  these results and s t a t i s t i c a l  
analysis  of the  data). A comparison was mride to  i l l u s t r a t e  t h e  
difference i n  corrosion protection between the urethane primer 
a t  1/10 m i l  and :I'IL-P-8585A a t  L / l O  m i l .  Both were topcoated 
with 5/10 m i l  WL-E-5556A Flat  Idhite Enamel. Referring t o  the  
salt spray exposure tests ( I l l u s t r a t i o n  Ill) note t h a t  no d i f -  
ference exists i n  the  body of the  panels. 
corrosion on panels primed with the  urethane primer i s  a t  the 
scratch marks. 
The only s l i g h t  
Contemporary t o  this ,  the  e f f e c t  of increasing d r i e r s  
was evaluated and the  addition of 16 pounds of Zirconium drier 
per 100 gallons (Zirconyl - 2 - Ethyl  Hexoate 28% - Advance 
Solvents) seemed t o  increase corrosion res i s tance  s igni f icant ly .  
With 1/10 mil of the urethane primer containing t h i s  d r i e r  there  
w a s  no corrosion a t  t he  scratch marks after two weeks i n  5% o r  
20% sal t  spray, 
Page 6 
However, we do not believe t h a t  we have s u f f i c i e n t  
s t a b i l i t y  information at  t h i s  time for inclusion of t h e  zir- 
conium drier i n  the primer formulation. 
This formulation w i l l  f u l f i l l  most of t he  reauire- 
ments sst fo r th  i n  I'ffL-P=eSB~A. Perhaps, the place where it 
i s  def ic ien t  i s  i n  the gloss reauirement. 
gloss of the urethane primer is 4 t o  6 u n i t s  and a t  5/10 m i l  
it i s  8 t o  10 uni t s ,  
mum a t  3/10 mil, 
y i e lds  sa t i s f ac to ry  s a l t  spray res i s tance  without topcoating, 
1/10 m i l  of t h i s  primer p l u s  5/10 m i l  of MIL-E-5556A forms a 
sy tem yielding good corrosion res i s tance  a t  a minimum weight, 
A t  1/10 mil the  
MIL-P-8585A requii-es 3 gloss  un i t s  maxi- 
Although a t  5/10 m i l  t h i s  urethane primer 
The urethane primer ( Sherwin-Tlilliams fosmuls 
nmber E90 !J C 9 )  should be reduced 200% with toluene f o r  
normal spray application. A medium spray coat w i l l  then 
deposit  s l i g h t l y  more than 1/10 m i l ,  
5'556A the primer should be dried six hours p r i o r  t o  topcoating 
with i.rrGS-5556A f o r  best results. 
Pgsuggested i n  MGE- 
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I?LLUSTTiATION #1 
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Page 8 
DATA #l 
1000 HCUZIS I N  SALT SPUY 3 
IA1 IB2 IC3 IIA2 IIB3 IICl IIIA3 IIIBl IIIC2 --------- 
5% 4 6 9  7 7 9 6 9 l o  
20$ 3 8 8  7 6 8 8 10 10 
STAT ISTICAL AXALSSIS 
5% Sal t  Spray 
Source 
Primers 
Primer Film Thickness 
Topcoat Fi’2-n Thickness 
Remaind-er 
Source 
Drimers 
Primer Film Thickness 
Toyoat  Film Thickness 
Remainder 
ss DF 18 Fobs Certainty - - -
6.2 2 3.3, 1.72 60% 
20.2 2 10.1 5.6 78% 
02 2 .1 e 5 6  35% 
3.6 2 1.8 
20% Sal t  Spray 
14s Fobs Certainty nF - --ss -
111.9 2 7.5 1.98 61% 
10.9 2 5.5 1.45 56% 
2.9 2 1.5 a 4  24% 
7.5 2 3.8 
It i s  s ignif icant  t h a t  t he  to9coat film thickness i s  not signi- 
f i can t  
3. See Technical Progress Report $4, October, 1964, f o r  a 
l i s t i n g  of the spec i f i c  variables. 


Development of corrosion inhibiting white primer final report, 26 jun. - 30 nov. 1964

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