Corrosion resistant, chromate-free conversion coating for magnesium alloys

A process for applying a chromate-free, corrosion resistant coating to a product formed from a magnesium based material, comprising the steps of:

• degreasing the product formed from the magnesium based material in a degreasing solution;
• cleaning the product formed from the magnesium based material in a highly alkaline cleaning solution;
• deoxidizing the product formed from the magnesium based material in a deoxidizing solution;
• and
• immersing the product formed from the magnesium based material in a solution containing phosphate and fluoride ions where a pH level of the solution is controlled in an approximate range of 5 to 7, the solution being provided with from 1.0 g/l to less than 2.0 g/l potassium permanganate and being maintained at a temperature of approximately 120 to 200 degrees Fahrenheit while immersing the product formed from the magnesium based material for a period of approximately 15 minutes to 90 minutes.

A process for applying a chromate-free, corrosion resistant coating to a product formed from a magnesium based material, comprising the steps of:

• degreasing the product formed from the magnesium based material in a degreasing solution;
• cleaning the product formed from the magnesium based material in a highly alkaline cleaning solution;
• deoxidizing the product formed from the magnesium based material in a deoxidizing solution;
• and
• immersing the product formed from the magnesium based material in a solution containing phosphate and fluoride ions where a pH level of the solution is controlled in an approximate range of 5 to 7, the solution being provided with from 1.0 g/l to 5.0 g/l of an active corrosion inhibitor and being maintained at a temperature of approximately 120 to 200 degrees Fahrenheit while immersing the product formed from the magnesium based material for a period of approximately 15 minutes to 90 minutes;
• and
• said phosphate and fluoride containing solution further containing 0.01 to 1.0 vol % of a surfactant.

A non-electrolytic process for applying a chromate free, corrosion resistant coating of at least magnesium phosphate and magnesium fluoride to a product formed from a magnesium alloy, comprising the steps of:

• degreasing the product formed from the magnesium alloy in a degreasing solution;
• cleaning the product formed from the magnesium alloy in a highly alkaline cleaning solution;
• deoxidizing the product formed from the magnesium alloy in a deoxidizing solution;
• providing a solution containing phosphate and fluoride ions, from about 0.3 to 0.5 wt % sodium bifluoride, and from about 1.0 g/l to 5.0 g/l of an active corrosion inhibitor selected from the group consisting of sodium tungstate, sodium vanadate, and mixtures thereof, and having a pH level in the range of 5 to 7;
• maintaining said solution at a temperature of approximately 120 to 200 degrees Fahrenheit;
• and
• immersing said product formed from said magnesium alloy in said solution for a time period in the range of 15 minutes to 90 minutes.

A process for applying a chromate free, corrosion resistant coating of at least magnesium phosphate and magnesium fluoride to a product formed from a magnesium alloy, comprising the steps of:

• degreasing the product formed from the magnesium alloy in a degreasing solution;
• cleaning the product formed from the magnesium alloy in a highly alkaline cleaning solution;
• deoxidizing the product formed from the magnesium alloy in a deoxidizing solution;
• providing a solution containing phosphate and fluoride ions, from about 0.3 to 0.5 wt % sodium bifluoride, and from about 1.0 g/l to 5.0 g/l of an active corrosion inhibitor selected from the group consisting of potassium permanganate, sodium tungstate, sodium vanadate, and mixtures thereof, and having a pH level in the range of 5 to 7;
• maintaining said solution at a temperature of approximately 120 to 200 degrees Fahrenheit;
• immersing said product formed from said magnesium alloy in said solution for a time period in the range of 15 minutes to 90 minutes;
• and
• said phosphate and fluoride containing solution further containing 0.01 to 1.0 vol % of a surfactant.

A non-electrolytic process for applying a chromate free, corrosion resistant coating of at least magnesium phosphate to a product formed from a magnesium alloy, comprising the steps of:

• degreasing the magnesium alloy product in a degreasing solution;
• cleaning the magnesium alloy product in a highly alkaline cleaning solution;
• deoxidizing the magnesium alloy product in a deoxidizing solution;
• providing a coating solution containing phosphate and fluoride ions and being provided with a concentration of sodium bifluoride in a range of 0.3 to 0.5 wt % and a concentration of an active corrosion inhibitor selected from the group consisting of sodium tungstate, sodium vanadate, and mixtures thereof in a concentration of from 1.0 g/l to 5.0 g/l;
• maintaining the coating solution at a temperature of 120 to 200 degrees Fahrenheit;
• and
• immersing the magnesium alloy product in the coating solution for a time period in the range of 15 minutes to 90 minutes.

A process for applying a chromate free, corrosion resistant coating of at least magnesium phosphate to a product formed from a magnesium alloy, comprising the steps of:

• degreasing the magnesium alloy product in a degreasing solution;
• cleaning the magnesium alloy product in a highly alkaline cleaning solution;
• deoxidizing the magnesium alloy product in a deoxidizing solution;
• providing a coating solution containing phosphate and fluoride ions and being provided with a concentration of sodium bifluoride in a range of 0.3 to 0.5 wt % and a concentration of an active corrosion inhibitor selected from the group consisting of potassium permanganate, sodium tungstate, sodium vanadate, and mixtures thereof in a concentration of from 1.0 g/l to 5.0 g/l;
• maintaining the coating solution at a temperature of 120 to 200 degrees Fahrenheit;
• immersing the magnesium alloy product in the coating solution for a time period in the range of 15 minutes to 90 minutes;
• and
• said phosphate and fluoride containing solution further containing 0.01 to 1.0 vol % of a surfactant.

A solution for use in a process for forming a chromate-free, corrosion resistant coating on a product formed from magnesium or a magnesium alloy, comprising:

• said solution having phosphate and fluoride ions;
• said solution containing from 1.0 g/l to 5.0 g/l of an active corrosion inhibitor selected from the group consisting of sodium tungstate, sodium vanadate, and mixtures thereof;
• and
• said solution having a pH of 5 to 7.

A solution for use in a process for forming a chromate-free corrosion resistant coating on a product formed from magnesium or a magnesium alloy, comprising:

• said solution having phosphate and fluoride ions;
• said solution containing from 1.0 g/l to less than 2.0 g/l potassium permanganate;
• and
• said solution having a pH of 5 to 7.

A solution for use in a process for forming a chromate-free, corrosion resistant coating on a product formed from magnesium or a magnesium alloy, comprising:

• said solution having phosphate and fluoride ions;
• said solution containing from 1.0 g/l to 5.0 g/l of an active corrosion inhibitor selected from the group consisting of potassium permanganate, sodium tungstate, sodium vanadate, and mixtures thereof;
• said solution having a pH of 5 to 7;
• and
• said solution further comprising from about 0.1 to 1.0 vol % of a surfactant.