US2290170A - Method for inspecting coated surfaces - Google Patents

Description

July 21, 1942. I F. DIEFFENBACH 7 2,290,170

METHOD FOR INSPECTING COATED SURFACES Filed Oct. 8, 1940 Patented July 21, 1942 METHOD FOR INSPECTING COATED SURFACES Ferd Dieflenbach, Pittsburgh, Pa. Application October'8, 1940, Serial No. 360,246

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 3 Claims.

This invention described herein may be manu factured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates generally to a method for the inspection of protective coatings, but more particularly to the microscopic inspection of cross-sectional areas of coated surfaces.

One object of the invention is to provide a simple and effective method for preparing coated surfaces for the microscopic inspection of the adhesive union between the layers of said coatings and the surface over which they are spread.

Another object of the invention is to provide a simple, efiicient and economical method for preparing coated surfaces and exposing crosssectional areas thereof for microscopic inspection.

Another object of the invention is to provide a method for the study of paint and painted surfaces in a manner similar to metallography in which the structures of metals are microscopically inspected and studied With these and other objects in view this invention consists in certain novel details of construction, combination and arrangement of parts, to be more particularly hereinafter set forth and claimed.

Referring to the figures in which like parts are represented by similar reference characters:-

Fig. 1 is a perspective view illustrating separated uncoated inspection blocks;

Fig. 2 is a perspective view showing the inspection blocks united and coated on one surface;

.Fig. 3 is a perspective view illustrating the I blocks separated as in Fig. l, but with coated surfaces;

Fig. 4 is a side elevation showing an inspection block mounted upon the stage of a microscope; and

Fig. 5 illustrates an enlarged cross-section of the coatings as viewed through the eyepiece of the microscope.

Referring to Fig. 1 it will be noted that the apparatus comprises two inspection blocks Ill and I0 which are provided with smooth lateral surfaces, and are drilled respectively at II and II and I2 and I2 for the reception of bolts I3 and i3, which are adapted to detachably connect the blocks and hold them tightly united by means of the nuts l4 and I4 as shown in Fig. 2.

These testing blocks may be made of steel, aluminum, wood, plastic or any other suitable material depending on the type and quality of 55 by examination without reagents. Such examithe protective coating which is to be inspected or the material which it is desired to coat. so as to ascertain the adhesive qualities of the coating with respect to said material.

After connecting the blocks l0 and Ill and fastening them tightly together by screwing up on the nuts l4 and I 4, one of the lateral surfaces extending over both of the blocks I0 and I0, is given one or more coats of paint, varnish, enamel or other protective coating which it is desired to inspect, as indicated by the numeral l5, Fig. 2.

After the coating or coatings l5 have completely dried the nuts I4 and M are unscrewed from the bolts l3 and I3 and the blocks Ill and I0 separated as shown in Fig. 3, thus splitting the coated surface along a central edge, as indicated by the numerals l6 and I6.

One of these blocks Ill or ID is then placed on the stage l'l (Fig. 4) of a microscope l8 with the split edge It ofthe coated surface I5 directly beneath the objective lens (not shown), and the microscope adjusted and focused in the usual manner for microscopic inspection of the crosssuch as the following:

(a) Adhesion between successive coats of paint in a paint system seems to be partially dependent upon the interlock of pigment particles. This explains, at least partially, the very decided lack of adhesion between dissimilar coatings ina paint system,

(b) The structure of certain paint films are heterogeneous throughout their thicknesses, the study of which is very important in that a paint film, particularly under water, must be stable throughout its thickness.

(0) The reason for the blistering of paints containing certain amounts of zinc yellow has been discovered.

The technique involved in the use of this device may be diversified in many ways. The

cross-sections are studied similarly to metal-v lography specimens, that is, by treating with various reagents to etch or react with various constituents of the paints to be studied. However, much can be determined with this device face of two adjoining detachably connected inspection blocks, allowing the coating to dry and then separating said blocks to fracture the coating along the line oi jointure of said blocks to expose cross-sectional areas of the divided coating.

a A method for determining the adhesive thereof comprising, coating a common plane sur- I qualities of coated surfaces comprising, coating a common plane surface of two adioining detachably connected inspection blocks, allowin the coating to dry, separating said blocks to fracture the coating along the line of jointure of said blocks and placing a cross-sectional area of the divided coating in the field of a microscope for inspection of the internal structure of the coating along the ruptured edge.

3. A. method. for preparing coated surfaces for 'microscopic inspection comprising, coating a continuous surface of two adjoining detachably connected inspection blocks, allowing the coating to dry' and then separating said blocks to fracture the coating along the lineof jointure of said blocks to expose cross-sectional areas of the divided'coating.

FERD DIEFFENBACH.

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