Environmentally friendly aluminum coatings as sacrificial coatings for high strength steel alloys

Patent metadata

Field	Value
Publication number	US-2016319449-A1
Application number	US-201615137965-A
Country	US
Kind code	A1
Filing date	Apr 25, 2016
Priority date	Apr 28, 2015
Publication date	Nov 3, 2016
Grant date	—

Abstract

Electroplating process is described for coating a ferrous alloy steel cathode substrate with an aluminum coating, the process comprises: a) immersing an aluminum anode substrate in a plating bath formulation comprising: a source of aluminum, an ionic liquid, a brightening agent, and a metal-salt compound; b) etching the cathode substrate by immersing it into the aluminum plating bath and conducting an anodic polarization step; c) electroplating the etched cathode substrate with the aluminum plating bath formulation; and d) rinsing with alcohol and water, and drying. Preferably, the process further comprises a heat treatment applied to the aluminum coated ferrous steel alloy obtained in step d).

First claim

1 . An electroplating process for coating a ferrous alloy steel cathode substrate with an aluminum coating, characterised in that the process comprises:
immersing an aluminum anode substrate in an aluminum plating bath formulation comprising:
a source of aluminum,
an ionic liquid,
a brightening agent, and
a metal salt;
etching a ferrous steel alloy cathode substrate by immersing it into the aluminum plating bath formulation and performing an anodic polarization; electroplating the etched ferrous alloy steel cathode substrate with the aluminum plating bath formulation, to form an aluminum coated ferrous steel alloy, wherein electroplating is carried out with a current density ranging from 1 mA/cm 2 to 100 mA/cm 2 , at a temperature ranging from 20° C. to 100° C. and under a dry inert gas; and rinsing the aluminum coated ferrous steel alloy.

2 . The electroplating process of claim 1 , wherein the ferrous alloy steel is a high strength steel alloy.

3 . The electroplating process of claim 1 , wherein the source of aluminum is an aluminum halide.

4 . The electroplating process of claim 1 , wherein the ionic liquid is a nitrogen-containing compound selected from N-alkyl-pyridinium salts, N-alkyl-N′-alkyl′ imidazolium salts, N-alkyl-N-alkyl′ pyrrolidinium salts, N-alkyl-N-alkyl′ piperidinium salts, quaternary ammonium salts and combinations thereof.

5 . The electroplating process of claim 4 , wherein the counter-anion of the nitrogen-containing compound is a halide, and the cation is selected from N-alkyl-N′-alkyl′ imidazolium (I) and N-alkyl-N-alkyl′ pyrrolidinium (II), wherein the substituents R and R′ independently represent an alkyl group.

6 . The electroplating process of claim 1 , wherein the brightening agent is selected from the group consisting of 1,10-phenanthroline, phthalazine, saccharin, isoniazid, coumarin, isonicotinic acid, nicotinic acid, 3,4-(methylenedioxy)toluene, 1,4-butynediol, 2-aminothiazole, 2-mercaptothiazoline, 1-methylimidazole and combinations thereof.

7 . The electroplating process of claim 1 , wherein the metal salt is an alkali-metal halide.

8 . The electroplating process of claim 1 , wherein the aluminum plating bath formulation consists of:
from 95.30 to 99.95 wt % of a mixture of aluminum trichloride and 1-ethyl-3-methylimidazolium chloride, wherein both components are present in the mixture in a molar ratio ranging from 80:40 to 60:40; from 0.01 to 1.0 wt % of 1,10-phenanthroline; and from 0.04 to 3.7 wt % of KCl.

9 . The electroplating process of claim 1 , wherein the electroplating step is carried out with a current density ranging from 5 mA/cm 2 to 25 mA/cm 2 , a temperature ranging from 40° C. to 75° C. and stirring the electrolyte at a range from 500 rpm to 1000 rpm.

10 . The electroplating process of claim 1 , wherein an aluminum anode substrate is subject to a pre-treatment step comprising:
mechanical polishing an aluminum anode substrate; alkaline cleaning the polished aluminum substrate followed by water rinsing; deoxidizing the cleaned aluminum substrate followed by water rinsing; and drying the deoxidized aluminum substrate to obtain a polished, clean, deoxidized and dry aluminum anode substrate.

11 . The electroplating process of claim 1 , wherein the ferrous alloy steel cathode is subject to a pre-treatment comprising:
degreasing an steel alloy substrate, and dry-blasting the degreased steel alloy, followed by removing any powder remaining in the surface of the stripped steel alloy to obtain a degreased and blasted ferrous steel alloy cathode substrate.

12 . The electroplating process of claim 1 , further comprising heat treating the aluminum coated ferrous steel alloy.

13 . The electroplating process of claim 12 , further comprising applying a conversion coating to the aluminum coated ferrous steel alloy obtained by the heat treating or the rinsing, wherein the conversion coating is selected from a hexavalent chromium conversion coating or a chromium free conversion coating.

14 . An aluminum coated ferrous steel alloy obtained by:
immersing an aluminum anode substrate in an aluminum plating bath formulation comprising:
a source of aluminum,
an ionic liquid,
a brightening agent, and
a metal salt;
etching a ferrous steel alloy cathode substrate by immersing it into the aluminum plating bath formulation and performing an anodic polarization; electroplating the etched ferrous alloy steel cathode substrate with the aluminum plating bath formulation, to form an aluminum coated ferrous steel alloy, wherein electroplating is carried out with a current density ranging from 1 mA/cm 2 to 100 mA/cm 2 , at a temperature ranging from 20° C. to 100° C. and under a dry inert gas; and rinsing the aluminum coated ferrous steel alloy.

15 . Use of the aluminum coated ferrous steel alloy of claim 14 in aeronautical, automotive, marine, construction, industrial and household applications.

16 . An aluminum plating bath formulation comprising:
an aluminum halide; a nitrogen-containing compound selected from N-alkyl-N′-alkyl′ imidazolium halide or N-alkyl-N-alkyl′ pyrrolidinium halide; a brightening agent; and an alkali metal halide.

17 . The aluminum plating bath formulation of claim 16 , comprising:
from 95.30 to 99.95 wt % of a mixture of aluminum trichloride and 1-ethyl-3-methylimidazolium chloride, wherein both components are present in the mixture in a molar ratio ranging from 80:40 to 60:40, from 0.01 to 1.0 wt % of 1,10-phenanthroline, and from 0.04 to 3.7 wt % of KCl.

Assignees

• Boeing Co

Inventors

• Izagirre Etxeberria Usoa
• Sanchez Cupido Laura
• Lapeña Rey Nieves
• Unzurrunzaga Ainhoa

Classifications

• C25D5/003

  Electroplating using gases, e.g. pressure influence · CPC title

• C25D17/10

  Electrodes {, e.g. composition, counter electrode} · CPC title

• C25D5/36

  of iron or steel · CPC title

• C25D5/52

  by brightening or burnishing · CPC title

• C25D3/665

  from ionic liquids · CPC title