NESC tech bulletin

National Aeronautics and Space Administration

www.nasa.gov

NASA Engineering and Safety Center Technical Bulletin No. 07-01

BraycoteTM Grease retains tribological properties

for 17 years in controlled storage

BraycoteTM greases that are in mechanisms in controlled storage retain their tribological proper-

ties for an extended period of time. Testing on aged and separated BraycoteTM grease obtained from 

several sources showed no detrimental effect on lubricity. Additionally, Thermal Gravimetric Analy-

sis testing demonstrated no significant decrease in performance due to static, controlled storage. 

Tribological action, heat, or other forces are required to effect the performance of BraycoteTM grease.

Applicability

BraycoteTM 601 grease on space flight and ground system 

mechanisms

Background

A scheduled inspection of the Rudder/Speed Brake actuators on 

Space Shuttle orbiter OV-103 revealed fretting corrosion, micro-

pitting, wear and discoloration of the lubricant BraycoteTM 601. 

A decision was made to replace the actuators with the existing 

spares, a single ship set which had been in controlled storage 

for the past 17 years. Data did not exist on the lubricity of Bray-

coteTM 601 grease after extended storage. 

Data and Analysis

Testing and analysis were undertaken to investigate

two key issues:

Issue 1: Oil separation of grease into its component oil and 

thickener is known to occur in storage. Its effect on lubric-

ity is not known.

Results: Lubricity testing was performed on aged grease, 

and grease that exhibited oil separation obtained from several 

sources, including grease that had been removed from the OV103 actuators. Three test protocols were used: (1) Falex Block 

on Ring; (2) Spiral Orbit Tribometer (SOT); and (3) Wedeven As-

sociates Machine (WAM) testing. In all cases, no detrimental 

effect on lubricity was observed due to storage and/or grease 

that experienced oil separation.

Issue 2: Chemical reactions involving the grease and the 

gear/housing material, 9310 steel, could lead to formation 

of Lewis acids, resulting in corrosion, pitting, and cracking.

The degree to which the chemical reactions were occurring 

in the actuators was unknown.

Results: Investigations into potential chemical reactions of the 

grease with the actuator steel were addressed in three ways: 

(1) an extensive literature review; (2) WAM testing to duplicate 

the conditions observed in the used actuators; and (3) Thermo-

dynamic analysis, using Thermal Gravimetric Analysis (TGA), 

to bound the amount of degradation/mass loss that might oc-

cur during 17 years of controlled storage. The literature review 

revealed that absent tribological action, i.e., no stress on the 

lubricant, no significant mass loss should occur below 190oC. 

The WAM testing was successful in duplicating the fretting cor-

rosion and micropitting effects observed on OV-103 by high fre-

quency low amplitude wear testing, thus reinforcing the results 

reported in the literature for similar material/lubricant combina-

tions. The TGA testing and thermodynamic analysis predicted 

no significant corrosive effects from static, controlled storage 

for 17 years.

References

Orbiter Rudder Speed Brake Actuator BraycoteTM Grease Inde-

pendent Technical Assessment/Inspection (ITA/I) Report, NESC 

RP04-03/03-003-E, May 2004

This work was led by Dr. Paul Munafo, Marshall Space Flight 

Center

For further information contact the NESC at www.nesc.gov

White BraycoteTM grease on top of a used actuator gear. The dis-

coloration present on the gear surfaces is normal for BraycoteTM 

grease in contact with steel.

NASA