Polymeric coating formulations and steel substrate composites

1. A process for making a composite work article suitable for fabricating rigid sheet metal components, comprising:

A) providing a steel sheet having opposed substantially planar first and second surfaces extending between opposite lateral edges;

B) pre-treating the first surface of the sheet to enhance reception and retention of a multi-layer polymeric coating on the pre-treated first surface;

C) transporting the sheet having the pre-treated first surface in-line at approximately ambient temperature;

D) melt extruding the multi-layer polymeric coating on the pre-treated first surface presented at the approximately ambient temperature to deposit an overlaying coating portion of substantially uniform thickness across the pre-treated first surface, and to deposit edge thickened overhang portions beyond the opposite lateral edges, the overhang portions having a thickness exceeding the substantially uniform thickness of the overlaying coating portion, the multi-layer polymeric coating comprising a tie polymeric layer contacting the pre-treated first surface, and a finish-surface polymeric layer;

E) solidifying the extruded multi-layer polymer coating, including the overhang portions;

F) trimming the solidified overhang portions beyond each of the lateral edges to leave the overlaying coating portion of substantially uniform thickness across the pre-treated first surface; and

G) subjecting the extruded multi-layer polymeric coating to a finish-treatment, comprising heating the extruded multi-layer polymeric coating at least to a melt temperature thereof, then cooling the multi-layer polymeric coating through a glass-transition temperature thereof at a sufficiently rapid rate to establish amorphous non-directional characteristics in the multi-layer polymeric coating.

2. The process of claim 1 , wherein the multi-layer polymeric coating further comprises an intermediate layer between and bonded to the tie polymeric layer and the finish-surface polymeric layer.

3. The process of claim 1 , further comprising electrolytic tin plating at least one surface of the steel sheet.

4. The process of claim 1 , wherein steps (C), (D), (E), (F) and (G) are practiced in a continuous, in-line manner.

5. The process of claim 1 , further comprising:

formulating the tie polymeric layer from a formulation comprising a maleic anhydride modified polypropylene (PP) layer, and

formulating the finish-surface polymeric layer from a formulation comprising about 5 weight percent polybutylene (PB).

6. The process of claim 5 , wherein the multi-layer polymeric coating further comprises an intermediate layer between and bonded to the tie polymeric layer and the finish-surface polymeric layer, and further wherein the intermediate layer is formulated from a controlled percentage of polybutylene and a member selected from the group consisting of

(i) a homopolymer polypropylene;

(ii) an ethylene/PP random copolymer, and

(iii) a combination of (i) and (ii).

7. The process of claim 6 , wherein the finish-surface polymeric layer is formulated from thermoplastic polymers that provide self-lubricating properties for end-usage product fabrication, the thermoplastic polymers comprising the about five percent PB, and a remainder selected from the group consisting of:

(i) a homopolymer polypropylene (PP),

(ii) an ethylene/PP random copolymer; and

(iii) a combination of (i) and (ii).

8. The process of claim 7 , wherein the controlled percentage of the polybutylene is from about ten percent to about twenty-five percent of the polybutylene, and wherein the intermediate layer is further formulated to include an effective percentage of titanium oxide (TiO 2 ) to act as a coloring agent.

9. The process of claim 1 , further comprising subjecting the first planar surface to a corrosion-protection technique selected from the group consisting of:

(i) electrolytic tin plating,

(ii) a cathodic dichromatic passivation coating, and

(iii) a combination of (i) and (ii).

10. The process of claim 9 , further comprising subjecting the second planar surface to the electrolytic tin plating to provide a tin plating weight in a range of about 0.25 pound per base box to about 1.25 pound per base box of plated surface area.

11. The process of claim 1 , further comprising subjecting each of the first and second planar surfaces to direct electrolytic tin plating to provide a tin plating weight of about 0.25 pound per base box of plated surface area.

12. The process of claim 1 , wherein the approximately ambient temperature is in a range of 75° F. to about 150° F.

13. The process of claim 1 , wherein said trimming of the solidified overhang portions is performed at each of the lateral edges.