Method of sealing an anodized metal article
A method of coating a metal article is disclosed that includes immersing a metal article having an exterior anodized layer in a bath containing a chemically active corrosion inhibitor, and applying a voltage to the article during the immersing, the voltage driving the chemically active corrosion inhibitor from the bath into the exterior anodized layer. An article is also disclosed that has a substrate comprising a metal, and a porous anodized layer formed on an exterior surface of the substrate that is infiltrated with a chemically active corrosion inhibitor, the anodized layer having an inward-facing region and an outward-facing region, the anodized layer having a greater concentration of chemically active corrosion inhibitors in the inward-facing region than in the outward-facing region.
1. A method of coating a metal article, comprising:
exposing a metal article having an exterior anodized layer to a plurality of chemically active corrosion inhibitors through immersion in at least one bath; and
applying a voltage to the article during the immersion using pulse rectification of an alternating current (AC) waveform, the voltage driving the plurality of chemically active corrosion inhibitors from the at least one bath into the exterior anodized layer;
the voltage driving a first one of the plurality of chemically active corrosion inhibitors to a greater depth into the metal article than a second one of the plurality of chemically active corrosion inhibitors; and
wherein the plurality of chemically active corrosion inhibitors are different from each other and are selected from the group consisting of permanganate ions, vanadate ions, tungstate ions, ZrF 6 2− , CrF 6 3− , citrate ions, Ce 2 (MoO 4 ) 3 , ZnMoO 4 , CaMoO 4 , cerium citrate, MgSiO 3 , ZnSiO 3 , CaSiO 3 , Cr(OH) 3 , ZrO 2 , NbO x , ZnO 2 , CoO x , PO 4 3− , SiO 3 2− , B 2 O 4 2− , Ce 3+ , Y 3+ , La 3+ , Pr 3+ /Pr 2+ , VO 4 3− , and WO 4 2− .
2. The method of claim 1 , wherein after the exposing and applying steps are complete, a concentration of the chemically active corrosion inhibitor is greater in an inward-facing region of the anodized layer than in an outward-facing region of the anodized layer.
3. The method of claim 1 , wherein the plurality of chemically active corrosion inhibitors comprise anions, and the voltage is a positive bias on the article.
4. The method of claim 1 , wherein the plurality of chemically active corrosion inhibitors comprise cations, and the voltage is a negative bias on the article.
5. The method of claim 1 , wherein the plurality of chemically active corrosion inhibitors comprise both anions and cations in a single bath, and said applying a voltage to the article comprises alternating between application of a positive voltage to drive the anions into the exterior anodized layer and a negative voltage to drive the cations into the exterior anodized layer during the immersion.
6. The method of claim 5 , wherein the positive voltage and negative voltage are part of the alternating current (AC) waveform.
7. The method of claim 1 , wherein a duration of the applying step is approximately 2-5 minutes, and the voltage is between approximately 3 volts 60 volts.
8. The method of claim 1 , wherein the voltage is between approximately 10 volts-15 volts.
9. The method of claim 1 , wherein said exposing and applying are performed for a first bath containing the first one of the plurality of chemically active corrosion inhibitors using a first voltage, and are separately performed for a second bath containing the second one of the plurality of chemically active corrosion inhibitors using a second voltage, such that the first one and the second one of the plurality of chemically active corrosion inhibitors are driven into the exterior anodized layer.
10. The method of claim 9 , wherein a duration of the applying step in each bath is approximately the same, and the voltages used during each applying step are approximately the same.
11. The method of claim 1 , wherein the first one or the second one of the plurality of chemically active corrosion inhibitors comprises a nanoparticle pigment, and the at least one bath comprises a colloidal solution in which the nanoparticle pigment is suspended.
12. The method of claim 1 , wherein at least one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of Ce 2 (MoO 4 ) 3 , ZnMoO 4 , CaMoO 4 , CaSiO 3 and Cr(OH) 3 .
13. The method of claim 1 , wherein at least one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of MgSiO 3 , ZnSiO 3 , CaSiO 3 , and SiO 3 2 .
14. The method of claim 1 , wherein:
one of the first and second one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of Ce 2 (MoO 4 ) 3 , ZnMoO 4 , CaMoO 4 , CaSiO 3 and Cr(OH) 3 ; and
the other of the first and second one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of MgSiO 3 , ZnSiO 3 , CaSiO 3 , and SiO 3 2− .
15. The method of claim 1 , wherein at least one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of B 2 O 4 2− , La 3+ , Pr 3+ /Pr 2+ , and VO 4 3− .
16. The method of claim 1 , wherein:
one of the first and second one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of Ce 2 (MoO 4 ) 3 , ZnMoO 4 , CaMoO 4 , CaSiO 3 and Cr(OH) 3 ; and
the other of the first and second one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of B 2 O 4 2− , La 3+ , Pr 3+ /Pr 2+ , and VO 4 3− .
17. The method of claim 1 , wherein:
one of the first and second one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of MgSiO 3 , ZnSiO 3 , CaSiO 3 , and SiO 3 2− ; and
the other of the first and second one of the plurality of chemically active corrosion inhibitors is selected from the group consisting of B 2 O 4 2− , La 3+ , Pr 3+ /Pr 2+ , and VO 4 3− .