Intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) resistance improvement method for metallic alloys

• US 9,079,211 B1
• Filed: 04/07/2014
• Issued: 07/14/2015
• Est. Priority Date: 12/31/2013
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Deshpande, Nishkamraj U., Barsun, H. Fred, Clark, Steven D.
• Primary Examiner(s): Deo, Duy
• Application Number:
  US14/246,797
• Publication Number:
  US 20150182996A1
• Time in Patent Office: 463 Days
• US Class Current: 1/1
• CPC Class Codes: C22C 21/00 Alloys based on aluminium
• CPC Class Codes: C22C 21/06 with magnesium as the next major constituent

Abstract

A method, structure, and/or material composition associated with overetching a structure or allow of interest to deplete magnesium content at and in a vicinity of grain boundaries which mitigates or prevents corrosion including, for example, intergranular corrosion (IGC) and/or intergranular stress corrosion cracking (IGSCC). Another aspect of the invention can include a process and material composition associated with providing a particular coating having a number of material properties. Additional steps, material composition(s), and/or exemplary structure(s) can also be provided which provides a nano coating over the depletion zone having a first coating in accordance with another embodiment of the invention.

Claims

1. A method comprising:

depletion of a β

-phase precipitate forming magnesium containing material from one or more surface layers at and in a vicinity of one or more grain boundaries associated with a part or work piece;

applying hydrophobic, electrically semi conductive/insulative, thermally insulative material coating to reduce a heat transfer property of the part or work piece with an effect of reducing diffusion of magnesium atoms at one or more said grain boundaries located beneath the part or work piece'"'"'s surface;

providing coating layer(s) having nano capsules containing adhesive fluid which would seal or fill in grain boundary cracks that can arise in a part or work piece'"'"'s surface during its service life.

2. A method of claim 1, wherein said depletion step comprises a material overetching step and said applying of said material coating process step so as to fill the grain boundary areas.

3. A method comprising:

overetching grain boundaries of an area or areas of a part or work piece'"'"'s to reduce a magnesium content in one or more surface grain boundary and its vicinity areas;

cleaning the overstretched grain boundaries area or areas of said part or work piece; and

applying a hydrophobic, electrically semi/insulative, thermally insulative, hard, galvanically compatible coating material layer or layers on the overetched grain boundary/boundaires of said area or areas having grain boundary network and grains;

providing coating layer(s) having nano capsules containing adhesive fluid which would seal or fill in grain boundary cracks that can arise in a part or work piece'"'"'s surface during its service life.