Method of analyzing corrosion and corrosion prevention

• US 6,258,252 B1
• Filed: 07/15/1998
• Issued: 07/10/2001
• Est. Priority Date: 07/16/1997
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Aoki, Shigeru, Takayama, Hirokazu, Miyasaka, Matsuho, Amaya, Kenji
• Primary Examiner(s): Bell, Bruce F.
• Application Number:
  US09/115,694
• Time in Patent Office: 1,091 Days
• Field of Search: G01/N.1704
• US Class Current: 205/775.5
• CPC Class Codes: G01N 17/02 Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement

Abstract

An object to be analyzed for corrosion and corrosion prevention is divided into a plurality of adjacent regions of plural types by a dividing plane, with one of the adjacent regions being referred to as an attentional region with a boundary as the dividing plane and the other as a non-attentional region with a boundary as the dividing plane. An initial current density or an initial potential is imparted to each element of the boundary of the non-attentional region to effect a boundary element analysis for determining a relationship between a potential and a current density in each the element. A potential distribution and a current density distribution in the attentional region in its entirety are determined, using the relationship between the potential and the current density in each the element of the boundary of the non-attentional region as a boundary condition for the attentional region.

Claims

1. A method of predicting corrosion and corrosion prevention of an object, comprising the steps of:

selecting an object having three dimensional structure to be analyzed, said object being made of metal and used in a solution having electric conductivity;

dividing said object into a plurality of adjacent regions of plural types by a dividing plane, with one of the adjacent regions being referred to as an attentional region with a boundary as said dividing plane and the other as a non-attentional region with a boundary as said dividing plane;

imparting a current to produce an initial current density or an initial potential to each element of the boundary of the non-attentional region to effect a boundary element analysis for determining a relationship between a potential and a current density in each said element;

determining a potential distribution and a current density distribution in said attentional region in its entirety, using said relationship between the potential and the current density in each said element of the boundary of the non-attentional region as a boundary condition for the attentional region, whereby the boundary condition for the attentional region is equal to a boundary condition of the non-attentional region;

effecting an element analysis on said non-attentional region to determine a potential distribution and a current density distribution in said non-attentional region in its entirety, using said relationship between the potential and the current density in each element of the boundary of the attentional region as a boundary condition for the non-attentional region, thereby a potential distribution and a current density distribution across the regions can continuously be analyzed; and

using said potential distribution and said current density distribution for predicting corrosion and corrosion prevention of said object.

2. A method according to claim 1, wherein said regions of plural types include regions which can be modeled in two-dimensional, three-dimensional, and axially symmetric open and closed spaces.

3. A method according to claim 2, further comprising the steps of:

extracting a candidate region which is axially symmetric;

modeling the extracted region into a pipe having a radius R at a dividing plane A;

imparting a current density distribution expressed by a delta function having an intensity a to the modeled pipe at r=R on a plane z=0;

analytically determining a potential φ

in the pipe; and

determining a position z where the magnitude of a change of the potential φ

is smaller than an allowable value to determine a region which can be modeled axially symmetrically.

4. A method according to claim 1, wherein said initial current density or said initial potential imparted to each element of the boundary of the non-attentional region is uniform.

5. A method according to claim 1, wherein said regions include at least two non-attentional regions present contiguously to one attentional region.