ABSTRACT

Nanolaminar electrodeposited zinc nickel alloys have demonstrated a performance up to 10x greater than standard zinc-nickel coatings. This performance is due to the unique microstructure and grain size of the alloys in the range of 25 to 100nm, which impart increased strength, hardness, and corrosion resistance.

This paper will give a brief overview of the nanolaminar deposition process and will present data on extended ASTM(1) B117 Salt Fog data, comparing various grades of nanolaminar zinc-nickel to a standard electroplated zinc-nickel coatings.1 In addition to this, the nanolaminate coatings will be characterized metallurgically to support and define the reasons for the greater corrosion resistance and overall performance of the coatings. This will be supported by data from field trials conducted in the areas of the Oil & Gas industry that have frequent failures due to corrosion. Further developments and improvements will also be detailed that open the application of the technology both to existing and new industrial applications.

INTRODUCTION

Nanolaminar or nanostructured zinc-nickel electrodeposited coatings are compliant with the composition requirements of ASTM B841 and F1941 (12 to 16% Ni: balance Zn).2,3 The term nanolaminar refers to the successive thin layered deposition of nanostructured grains (≈ 25nm); accomplished by modulating the electrodeposition into a waveform applied at defined time periods and varying current densities. Standard electroplating in contrast, applies a continuous DC current throughout the electrodeposition process, resulting in grains that while initially fine will coarsen as a function of thickness ranging to the micrometer range.

Like the standard zinc-nickel coatings, nanostructured zinc-nickel coatings gain their corrosion resistance by providing a barrier to the atmospheric corrosion environment and by acting as a sacrificial galvanic coating that sacrifices itself by interacting with humidity to protect the metals substrate. By reviewing the factors that contribute to the microstructure and properties of standard zinc-nickel coatings, it will be possible to form a basis of comparison of how the nanolaminar coatings differ and how these differences in terms of electrodeposition processing and microstructure variations may impact performance.

Keywords:
upstream oil & gas, corrosion management, subsurface corrosion, coating, well integrity, nickel mining, materials and corrosion, riser corrosion, production chemistry, pipeline corrosion
Subjects:
Production Chemistry, Metallurgy and Biology, Pipelines, Flowlines and Risers, Materials and corrosion, Well Integrity, Subsurface corrosion (tubing, casing, completion equipment, conductor), Corrosion inhibition and management (including H2S and CO2)
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