Two-step chemical/electrochemical process for coating magnesium alloys

Patent · Tue Aug 31 00:00:00 EDT 1993

OSTI ID:5987352

Bartak, D E; Lemieux, B E; Woolsey, E R

A process is described for forming an improved corrosion resistant coating on a magnesium-containing article, which process comprises: (a) treating the article with a first aqueous solution, at a pH of about 5 to 8 and a temperature of about 40 to 100 C, which solution comprises about 0.2 to 5 molar ammonium fluoride to create a metal ammonium fluoride-containing layer on the article to form a pretreated article; (b) placing the pretreated article into a second aqueous solution having a pH of at least about 12.5 which comprises: (i) about 2 to 12 g/L of an aqueous soluble hydroxide; (ii) about 2 to 15 g/L of an aqueous soluble fluoride-containing composition selected from the group consisting of fluorides, fluorosilicates, and mixtures thereof, and (iii) about 5 to 30 g/L of an alkali metal silicate; (c) establishing a voltage differential between an anode comprising the pretreated article and a cathode in the second solution of at least about 100 volts to create a current density of about 2 to 90 mA/cm[sup 2]; wherein a silicon oxide-containing coating is formed on the article.

• Assignee: Technology Applications Group, Inc., Grand Forks, ND (United States)
• Patent Number(s): US 5240589; A
• Application Number: PPN: US 7-918946
• OSTI ID: 5987352
• Resource Relation: Patent File Date: 22 Jul 1992
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MAGNESIUM ALLOYS
PROTECTIVE COATINGS
SILICON OXIDES
CHEMICAL COATING
AMMONIUM FLUORIDES
AQUEOUS SOLUTIONS
HYDROXIDES
PH VALUE
SILICATES
ALLOYS
AMMONIUM COMPOUNDS
AMMONIUM HALIDES
CHALCOGENIDES
COATINGS
DEPOSITION
DISPERSIONS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
MIXTURES
OXIDES
OXYGEN COMPOUNDS
SILICON COMPOUNDS
SOLUTIONS
SURFACE COATING
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication