155MM Spindle Corrosion Improvement Program (SCIP)

NCMS Project #: 140478

Problem: The 155MM Howitzer breech spindles are coated with thin electroplated high contraction chrome (HC Cr) to protect the substrate 4340 steel component for extended cycle life.  However, issues with the electroplated HC Cr coatings include non-uniformity, and the coating flakes off which leads to a propensity for cracks allowing water and other chemicals to penetrate the coatings to corrode the substrate armament components.  In its current application, the spindles need to meet operating interface requirements with an obturator group (traps propellant gases from escaping) that seals the breech environment.  Corrosion and pitting problems compromises this seal requirement as well.  When chrome loss occurs, the spindles are condemned; when the obturator seal is broken, it is no longer safe to operate the breech.  This causes early condemnation, low firing EFCs, (effective full charge) and deterioration of the spindle fleet in operation as well as in storage, causing item management and logistic issues.


  • Provide a more uniform coating on the breech spindles than the current processes.
  • Resolve wear, erosion and corrosion issues along with providing opportunities to improve current production processes.
  • Reclaim and extend the service life of numerous armament system components.

Solution/Approach: The scope of this effort titled the Spindle Corrosion Improvement Program (SCIP) is to design and fabricate a prototype conforming anode system and associated tooling and fixturing for the electrodeposition of chromium plate plating coating on to the 155MM Howitzer spindles.  Prototype tooling, including anodes and racks will be designed such that it can be fully transitioned and implemented to the current production line at the Watervliet Arsenal.

Impact on Warfighter:

  • Improve reliability, sustainability, and safe operation of the breech system.

DOD Participation:

  • U.S. Army ARDEC (Benet Labs)

Industry Participation:

  • Advanced Tooling Corp.
  • CAI Resources
  • NCMS

Final Report