The corrosion behavior of oily film corrosion preventative compounds applied to 1018 steel

Open Access
Author:
Montgomery, Eliza Lauren
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
July 08, 2008
Committee Members:
  • Barbara Shaw, Committee Chair
  • Elzbieta Sikora, Committee Member
  • Howard W Pickering, Committee Member
  • Joseph Manuel Perez Sr., Committee Member
Keywords:
  • electrochemistry
  • FT-IR
  • corrosion preventative compounds
  • corrosion
  • corrosion inhibitor
  • oil film
  • 1018 steel
  • seawater
Abstract:
Many corrosion problems for Army transport vehicles initiate when the vehicles are transported through seawater environments for eventual active use. Exposure to highly-corrosive salt ions, namely chloride, that are abundant in these environments is nearly unavoidable during vehicle transport, and the resulting corrosion is often initiated on these vehicles before they are used in their intended application. Corrosion Preventative Compounds, referred to as CPCs, are a strategy used commonly as a temporary and outermost line of defense against corrosion during transportation and active use in the field. The protection that a CPC provides to the uncoated steel components is of interest because bare metal exposure is the most vulnerable path for the onset of corrosion in this corrosion system. Should the uncoated steel become subjected to seawater environments, the formation of corrosion product is quite rapid. This study focused on using surface-based characterization techniques to examine the role that three commercially-available oil-based CPC types played in protecting 1018 steel surfaces from corrosion initiation in artificial seawater environments. The CPCs used in this research were water-displacing oil-based liquids that cured to form nearly-dry films on the steel surfaces. Surface chemistry techniques, FT-IR and XPS, were used to examine the as-applied CPC films prior to and after exposure to the corrosive environment. Electrochemical and corrosion methods were used to monitor the stability and eventual degradation of the CPC films and the substrate as a function of time of exposure to the corrosive environment. This study resolved some uncertainties that surround the mechanisms of oil-based corrosion preventative compounds on low carbon steel. In general after initial immersion, the oil-based CPC films, hydrophobic by nature, acted as a temporary barrier to protect the substrate from the aqueous-based corrosion environment. After longer immersion times, the CPC films appeared to intermix with the initially-forming corrosion products to form an intermediate type of protective film that prevented the underlying substrate from further corrosion. Eventually, the CPC films degraded such that they no longer inhibited further corrosion. While similar in composition and general behavior, the three different CPC types provided varying degrees of protection from corrosion to the 1018 steel substrate in the artificial seawater environment.