Testing of High Corrosion Resistant Metallic Coatings for Tensioner Risers and Piston Rods Exposed to Marine Environments

Hydraulic riser tensioners (for offshore drilling platforms) and piston rods (for hydraulic systems) have been used in marine environments. They are exposed to a variety of severe operating conditions that range from marine atmospheres to splash zone. Traditionally, different substrates (typically Fe alloys) are coated either with a hard chromium, ceramic, or metallic coatings. Another alternative is using a highly alloyed steel or Ni alloy. Several of these combinations of materials have been successfully implemented. However, some of these materials have shown significantly lower corrosion and wear resistance in marine environments.

The present work describes the testing and qualification of piston rod materials taking into consideration the effect of the environment as well as the effect of the operation requirements. The accelerated corrosion testing as well as the wear testing aimed to select the best material for a given environment/application will be discussed. Characterization using electrochemical techniques, optical microscopy, AFM, SEM and EDS will also be disscused.

References:

1.      Haukås-Eide, O., K. Lønvik and K. P. Fischer, “Guideline for material selection and qualification of wear and corrosion protective hard face coatings for piston rods”, NACE 2007 Paper Number 07694, 2007.

2.      V. M. Salinas-Bravo and R. C. Newman, Corrosion Science, 36, (1994), 67.