GB2118458A

GB2118458A - Coating a metal surface so as to render it non-stick and abrasion-resistant

Info

Publication number: GB2118458A
Application number: GB08304274A
Authority: GB
Inventors: Harry Chapman Johnson
Original assignee: ARMOURCOTE SURFACE TREATMENTS
Current assignee: ARMOURCOTE SURFACE TREATMENTS
Priority date: 1982-04-20
Filing date: 1983-02-16
Publication date: 1983-11-02
Also published as: ZA832048B; ES521045A0; EP0092309A1; DE3232726A1; AU1259283A; DK394582A; GB8304274D0; ES8405083A1

Description

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GB 2 118 458 A

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SPECIFICATION

A method of coating a metal surface so as to render it non-stick and abrasion-resistant

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This invention relates to a method of coating a metai surface so as to render it non-stick and abrasion-resistant.

A known method of applying a non-stick coating to 10 the metal surface of an article includes the steps of preparing the surface in conventional manner to receive a sprayed coating of molten metal, spraying over said surface a coating of stainless steel or molybdenum to provide a continuous and imper-15 vious micro-crenellated intermediate surface with microscopic prominences and interstices, abrading said intermediate surface to remove any surface film such as oxide, applying a coating of a non-stick agent to the abraded surface and sintering or curing 20 the coating so as to provide a firmly bonded complete covering to the sprayed metal coating.

In the above method, the metal spray is applied to provide an impervious coat on top of which a layer of non-stick agent, usually P.T.F.E. (polytetrafluoro 25 ethylene), is applied. Due to the application of the metal spray, the finished coating lasts longer than a coating of P.T.F.E. applied directly onto the base metal. Nevertheless, in time, the P.T.F.E. coating is worn away from the surface of the sprayed-on metal 30 layer and the non-stick property of the surface diminishes.

An object of the present invention is to provide an improved method of applying a non-stick coating to a metal surface whereby the coating lasts consider-35 ably longer than hitherto.

With this object in view, the present invention provides a method of coating a metal surface so as to render it non-stick and abrasion resistant comprising the steps of sand or shot blasting the metal 40 surface, applying stainless steel or molybdenum to the surface so as to cover not less than 65% and not more than 90% thereof and provide a pervious intermediate substrate having a micro-crenellated surface, applying a primer coat to penetrate the 45 pervious substrate and finally applying a top coat, primarily of a non-stick agent, so as to form, upon the metal surface, a matrix of stainless steel or molybdenum impregnated with the non-stick agent.

The invention will be described further, byway of 50 example, with reference to the accompanying drawings, in which:

Figure 1 is a sectional elevation of a shot blasted metal surface;

Figure 2 is a similar section after application of a 55 steel or molybdenum coating; and

Figure 3 is a similar section to that shown in Figure 2 after the application of a coating including a non-stick agent to form an impregnated matrix.

In a preferred method in accordance with the 60 invention a base metal surface a to be rendered nonstick is firstly shot or sand blasted (Figure 1). Stainless steel or molybdenum is flame sprayed onto the base metal surface a so as to cover not less than 65% and not more than 90% of the metal 65 surface a and provide a pervious intermediate substrate b having a micro-crenellated surface (Figure 2). The thickness of the pervious substrate b is, for example, between 0.025 and 0.050 mm.

Once the intermediate pervious substrate b has 70 cooled, a primer of sufficiently low viscosity to penetrate said pervious layer is applied thereto and air or oven dried at about 120°C to 150°Cand allowed to cool. The primer may be aqueous-based or resin-based, the latter being used whenever a non-75 corrosible final non-stick surface is required. A suitable aqueous-based primer would be 10 parts P.T.F.E. to 1 part pigment and a suitable resin-based primer would be 20 parts resin to 24 parts pigment. It will, however, be appreciated that these are only 80 examples and many other mixtures or solutions of differing composition may be useful.

After the primer has dried and cooled, a second or top coat, consisting primarily of a non-stick agent such as P.T.F.E. orT.F.E./H.F.P. (Tetrafiuoroethylene/ 85 polyhexafluoropropylene), is applied thereover and stored at temperature of 200°C to 450°C for twenty to thirty minutes. A suitable top coat for use after an aqueous-based primer is 16 parts P.T.F.E. to 1 part pigment and a suitable top coat for use after a 90 renn-based primer, when a non-corroding suface is required, is 13 parts P.T.F.E. to 11 parts P.E.S. (polyethyl suiphore).

The non-stick agent c is able to penetrate right through the pervious substrate b to the metal 95 surface a. Figure 3 illustrates the resultant matrix of stainless steel or molybdenum b impregnated and coated with non-stick agent c upon the original metal surface a. This coating lasts considerably longer, i.e. is much more resistant to wear, than any previously 100 known non-stick coating.

Claims

1. A method of coating a metal surface so as to 105 render it non-stick and abrasion resistant comprising the steps of sand or shot blasting the metal surface, applying stainless steel or molybdenum to the surface so as to cover not less than 65% and not more than 90% thereof and provide a pervious 110 intermediate substrate having a micro-crenellated surface, applying a primer coat to penetrate the pervious substrate and finally applying a top coat, primarily of a non-stick agent, so as to form, upon the metal surface, a matrix of stainless steel or 115 molybdenum impregnated with the non-stick agent.

2. A method as claimed in claim 1 wherein the intermediate substrate is between 0.025 mm and 0.050 mm thick.

3. A method as claimed in claims 1 or 2 wherein 120 the primer coat applied to the pervious substrate is air or oven dried at 120°C- 150°C.

4. A method as claimed in any of claims 1 to 3, wherein the non-stick agent is P.T.F.E. or T.P.E/H.F.P. and the top coat applied to the primer layer is stoved

125 at a temperature of 200°C-450°C.

5. A non-stick and abrasion-resistant surface coating formed by the method claimed in any preceding claim.

6. A method of coating a metal surface so as to 130 render it non-stick and abrasion-resistant substan-

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GB 2 118 458 A

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tially as hereinbefore described.

7. A non-stick and abrasion-resistant surface coating as illustrated by Figure 3 of the accompanying drawing.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1983.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.