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

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).

What is claimed is: 
     
         1 . An electroplating process for coating a ferrous alloy steel cathode substrate, comprising:
 providing an aluminum plating bath formulation comprising a source of aluminum, an ionic liquid, phenanthroline, and KCl,   immersing an aluminum anode substrate in the aluminum plating bath formulation;   immersing the ferrous steel alloy cathode substrate in the aluminum plating bath formulation; and   electroplating an aluminum coating over the ferrous steel alloy cathode substrate.   
     
     
         2 . The electroplating process of  claim 1 , further comprising pre-treating the aluminum anode substrate by:
 mechanical polishing the aluminum anode substrate to form a polished aluminum anode substrate;   alkaline cleaning the polished aluminum anode substrate to form a cleaned aluminum anode substrate; and   deoxidizing the cleaned aluminum anode substrate to form a deoxidized aluminum anode substrate.   
     
     
         3 . The electroplating process of  claim 1 , further comprising pre-treating the strength ferrous steel alloy cathode substrate by:
 degreasing the ferrous steel alloy cathode substrate to obtain a degreased ferrous steel cathode substrate; and   dry-blasting the degreased ferrous steel alloy cathode substrate to obtain a stripped ferrous steel alloy cathode substrate.   
     
     
         4 . The electroplating process of  claim 1 , further comprising etching the ferrous steel alloy cathode substrate by performing an anodic polarization to form an etched ferrous steel alloy cathode substrate, wherein the aluminum coating is electroplated over the etched ferrous steel alloy cathode substrate. 
     
     
         5 . The electroplating process of  claim 1 , heat treating the aluminum coating electroplated over the ferrous steel alloy cathode substrate. 
     
     
         6 . An electroplating process for coating a ferrous alloy steel cathode substrate, comprising:
 providing an aluminum plating bath formulation, the aluminum plating bath formulation comprising:
 a source of aluminum and an ionic liquid; 
 from 0.01 to 1.0 wt % of the brightening agent of 1,10-phenanthroline; and 
 from 0.04 to 3.7 wt % of the metal salt of KCl; 
   immersing an aluminum anode substrate in the aluminum plating bath formulation;   immersing the ferrous steel alloy cathode substrate in the aluminum plating bath formulation; and   electroplating an aluminum coating over the ferrous steel alloy cathode substrate.   
     
     
         7 . The electroplating process of  claim 6 , wherein the source of aluminum is aluminum trichloride and the ionic liquid is 1-ethyl-3-methylimidazolium chloride, the aluminum plating bath comprising from 95.30 to 99.95 wt % a mixture of the aluminum trichloride and the 1-ethyl-3-methylimidazolium chloride in a molar ratio from 80:40 to 60:40. 
     
     
         8 . The electroplating process of  claim 6 , wherein the electroplating is carried out with a current density from 1 mA/cm 2  to 100 mA/cm 2 , at a temperature from 20° C. to 100° C. and under a dry inert gas. 
     
     
         9 . The electroplating process of  claim 6 , wherein the electroplating is carried out with a current density from 5 mA/cm 2  to 25 mA/cm 2 , a temperature from 40° C. to 75° C. and with stirring the aluminum plating bath formulation from 500 rpm to 1000 rpm. 
     
     
         10 . The electroplating process of  claim 6 , wherein the ferrous alloy steel cathode substrate is a high strength ferrous steel alloy cathode substrate containing between 0.2 and 0.5 wt % of carbon and not more than 8 wt % of alloying elements. 
     
     
         11 . The electroplating process of  claim 6 , wherein the source of aluminum is an aluminum halide. 
     
     
         12 . The electroplating process of  claim 6 , 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. 
     
     
         13 . The electroplating process of  claim 6 , further comprising applying a conversion coating to the aluminum coating over the ferrous steel alloy cathode substrate. 
     
     
         14 . The electroplating process of  claim 6 , further comprising pre-treating the aluminum anode substrate by:
 mechanical polishing the aluminum anode substrate to form a polished aluminum anode substrate;   alkaline cleaning the polished aluminum anode substrate to form a cleaned aluminum anode substrate; and   deoxidizing the cleaned aluminum anode substrate to form a deoxidized aluminum anode substrate.   
     
     
         15 . The electroplating process of  claim 6 , further comprising pre-treating the strength ferrous steel alloy cathode substrate by:
 degreasing the ferrous steel alloy cathode substrate to obtain a degreased ferrous steel cathode substrate; and   dry-blasting the degreased ferrous steel alloy cathode substrate to obtain a stripped ferrous steel alloy cathode substrate.   
     
     
         16 . The electroplating process of  claim 6 , further comprising etching the ferrous steel alloy cathode substrate by performing an anodic polarization to form an etched ferrous steel alloy cathode substrate, wherein the aluminum coating is electroplated over the etched ferrous steel alloy cathode substrate. 
     
     
         17 . The electroplating process of  claim 6 , heat treating the aluminum coating electroplated over the ferrous steel alloy cathode substrate. 
     
     
         18 . An aluminum coating formed over a ferrous alloy steel cathode substrate by:
 providing an aluminum plating bath formulation, the aluminum plating bath formulation comprising:
 a source of aluminum and an ionic liquid; 
 from 0.01 to 1.0 wt % of the brightening agent of 1,10-phenanthroline; and 
 from 0.04 to 3.7 wt % of the metal salt of KCl; 
   immersing an aluminum anode substrate in the aluminum plating bath formulation;   immersing the ferrous steel alloy cathode substrate in the aluminum plating bath formulation; and   electroplating an aluminum coating over the ferrous steel alloy cathode substrate.   
     
     
         19 . The aluminum coating of  claim 18 , wherein the aluminum coating is uniform, adherent, and levelled. 
     
     
         20 . The aluminum coating of  claim 18 , wherein the ferrous alloy steel cathode substrate is selected from a group consisting of an aeronautical cathode substrate, an automotive cathode substrate, a marine cathode substrate, a construction cathode substrate, an industrial cathode substrate, and a household cathode substrate.