GB2190858A

GB2190858A - Coating surfaces

Info

Publication number: GB2190858A
Application number: GB08621060A
Authority: GB
Inventors: Geoffrey John Landon-Browne
Original assignee: Smith Meters Ltd
Current assignee: Smith Meters Ltd
Priority date: 1986-04-25
Filing date: 1986-09-01
Publication date: 1987-12-02
Also published as: GB8621060D0; EP0243068A3; GB2190858B; EP0243068A2

Abstract

A jet of a mixture of abrasive material and powdered fusible paint is directed at the casing with sufficient energy to remove the rust and to cause the paint to fuse onto the surface. Preferably the mixture is 90% iron shot and 10% epoxy resin powder paint. The method may be used for coating other contaminated surfaces, e.g. surfaces having old flaking paint layers.

Description

GB 2 190 858 A 1 SPECIFICATION dislodged by the shot fails away so that it

does not become heated sufficiently to be fused to the epoxy Coating surfaces resin. It is only when the shot hits a solid surface which remains in placeto be repeatedly struck that This invention relates to coating surfaces having 70 the heating effect is sufficient forthe epoxy resin to contaminating material thereon, for instance, fuse to it. The time required forthis to be achieved corroded or rusty surfaces. depends on the degree of contamination of the Such surfaces have previously been prepared fora surface, buttypically is one second.

coating of paint orthe like by shot blasting sothat Itwill be appreciated thatthe debris removed at rust or other contaminating material is removed. 75 (14) will contain unused epoxy powder and re-usable According to the invention, a surface having shot. Thiswill normally be recovered by a cyclone or contaminating material thereon is coated with paint gravity separator (notshown) and re-used.

orthe like by a process in which a mixture of abrasive The requirement for the shot is to be hard enough material and powdered fusible coating material to removethe rust and to heatthe surface. Other impinges on the surface with sufficient energyto 80 materialsthan the iron shot referred to above removethe contaminating material and to heatthe capable of doing this may be used in the process.

surfaceto cause the coating material to fuse onto it. Thefunction of the epoxy resin is to fuse and form The mixture may be a major proportion byvolume a paint layer on the hotsurface. Othercoating of iron shot and a minor proportion of powdered materials capable of preparatino as a powder and of epoxy resin. The epoxy resin may include a pigment 85 fusing can also be applied using this process. For and comprise a paint. instance, plastics material films which need not be It will be appreciated thatthe cleaning and painting coloured can be applied to protectthe surface.

operations previously requiring two processes are The process may be used to repaint deteriorated carried out in the one process. surfaces with flaking paint which is removed bythe A specific example of the invention is now 90 shot and repainted in one action.

described with reference to the accompanying When a heavily greasy surface is to be processed, drawing, which shows in diagrammatic form an a degreasing operation may be required before apparatus in the process of coating a rusty casing. painting. Otherwisethe cleaning and painting is The casing (11) which is of pressed steel and has conducted in one operation with no external heating acquired a coating of rust in storage is placed at 95 required. Thus a considerable saving in time and room temperature in a compartment (12). A pressure energy is achieved.

jet (13) is directed to impinge on the casing, the jet The criteria determining the functioning of the picking up a mixture of chilled iron shot and an process are the size and hardness of the shot,the epoxy resin powder including a pigmentfrom a pressurewith which it is projected (i.e. itsvelocity), reservoir (15). The mixture impinges on the casing 100 the proportion of shotto powder, the ambient with sufficient kinetic energyto remove the rust temperature, and the melting point of the powder.

coating, which fails with spent material to be These are adjusted by experimentto achievethe removed at outlet (14). This bombardment also heats optimum resuitforthe degree of contamination the surface locallyto a temperature atwhich the being handled and the surface coating required.

epoxy resin powderfuses onto the surface and cures 105 The invention also extends to apparatus designed to form a paint film. The casing is rotated so that all to carry outthe process described above and to of its surface is treated, the whole process taking less items coated bythe process.

than a minute.

Claims

The proportion of shotto powder in this example CLAIMS is 90% byvolume of

shotto 10% of epoxy resin 110 powder. Other proportions may also be usedJor 1. A method of coating a surface having instance between 75%-95% of shot by volume. There contaminating material thereon with paint orthe should preferably be more shotthan powder. The jet like, wherein a mixture of abrasive material and (13) is directed by an air-operated gun (16) in which powdered fusible coating material is caused to air pressures of 80-90 lbs/sq. inch are used. The 115 impinge on the surface with sufficient energyto temperature to which the surface is heated is about remove the contaminating material and to heat the 1800C, at which the resin powder melts. It is, surface so that the coating material fuses onto it.

however, only achieved on the outer skin of the
2. A method as claimed in claim 1, wherein said casing while the bombardment takes place, and the abrasive material is iron shot.

casing cools rapidlywhen the bombardment ceases. 120
3. A method as claimed in claim 1 orclaim 2, Thus the rusty casing is placed in the wherein said coating material is epoxy resin.

compartment, processed, and is removed in a
4. A method as claimed in claim 3, wherein said painted, cured condition at a handlable temperature. epoxy resin comprises a paint.

No external heating is needed to heat the whole
5. A method as claimed in anyof claims 1 to4, casing for curing, snce the heat engendered by the 125 wherein said mixture comprises a major proportion impingement of the shot for cleaning the surface is by volume of abrasive and a minor proportion by used to fuse and cure the epoxy resin. When the volume of coating material.

mixture first meetsthe casing it is cold, so the epoxy
6. A method of coating a surface having resin hitting it does not stick. The shot part of the contaminating material thereon, in which a mixture mixture acts on the rustto remove it. Loose material 130of between 75%- 95% byvolume of iron shot and dry 2 GB 2 190 858 A 2 epoxy resin coating material is caused to impinge in a jet of air onto the surface with sufficient energyto remove the contaminating material and cause the coating material to adhere to the surface.
7. Amethod as claimed in anyof claims 1 to6, wherein said mixture comprises 90% byvolume of abrasive.
8. A method as claimed in anyof claims 1 to7, wherein said mixture is caused to impinge on the surface in a jet airfrom an air-operated gun using air pressures of 80- 90 lbs/square inch.
9. A method as claimed in anyof claims 1 to8, wherein the spent mixture is recovered, separated and re-used.
10. A method of coating a surface having contaminating material thereon substantially as described hereinbefore with reference to the accompanying drawing.
11. Apparatus adapted for carrying out the method asclaimed in anyof claims 1 to 10.
12. An item coated bythe method as claimed in any of claims 1 to 10.
13. An item of steel coated by the method as claimed in any of claims 1 to 10.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd, 10187, D8991685. Published byThe PatentOffice, 25 Southampton Buildings, London, WC2A 1 AY, frornwhich copies may be obtained.