CA1272395A - Apparatus and method for adhesive testing of coatings - Google Patents

Apparatus and method for adhesive testing of coatings

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Publication number
CA1272395A
CA1272395A CA000508119A CA508119A CA1272395A CA 1272395 A CA1272395 A CA 1272395A CA 000508119 A CA000508119 A CA 000508119A CA 508119 A CA508119 A CA 508119A CA 1272395 A CA1272395 A CA 1272395A
Authority
CA
Canada
Prior art keywords
dolly
coating
bonding
ram
piston
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000508119A
Other languages
French (fr)
Inventor
William H. Thomason
Randall G. Ivie
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ConocoPhillips Co
Original Assignee
Conoco Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Conoco Inc filed Critical Conoco Inc
Priority to CA000508119A priority Critical patent/CA1272395A/en
Application granted granted Critical
Publication of CA1272395A publication Critical patent/CA1272395A/en
Expired legal-status Critical Current

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  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Abstract

Abstract Of The Disclosure Disclosed is an apparatus for applying a consistantly perpendicular tension force to a dolly for testing of the adhesive bond strength between a coating and a substrate The tester comprises a ram passing through an axially centered opening in A dolly bonded to the coating. Piston and cylinder means are associated with the ram and the dolly so that pressure within the piston chamber formed thereby causes the development of a tension force within the dolly which is perpendicular to the coating being tested because of its coaxially centered orientation with respect to the ram.

Description

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APPARAT S AND METHOD FOR ADHESION TESTING OF COATINGS

This invention xelates to~the art oE materials testing and, more particularly, to an improved apparatus for the testing of coating adhesion to a substrate.
Background Of The Inventlon For many applications, the adhesion of an exterior coating to a subs-trate is e~tremely critical. Whether the coating is for electrochemical protection such as an anodic coating of flame sprayed aluminum on a steel offshore structure or for providing passive protection such as a paint coating acting as a barrier against a corrosive environ-ment, it is critical that the adhesion of the coating to the substrate be within well defined limits~ depending on the application, in order to provide the requisite protection desired of the coating. ~ny protective advan~age afforded by a coating is quickly lost when the coating separates from the substrate.
In order that the tests be reliably reproducible, it is essential that an adhesion tester apply purely tensile ~, 20 forces to the coating which are in a direction perpendicular `~ to the coated surface. Any nonperpendicularly directed forces can result in tearing of the coating and an inaccurate adhesion test reading.
U.S. Patent Number 3,821,892 describe~ an apparatus for testing intercoat adhesion. A clolly is bonded to the test material and a tractive force i~ applied to the dolly which is located between a two-legged support, the legs bearing against the coated surface~ While this apparatus is adequate for testing coatings on a completel~ ~lat surface~ any localized irregularities within the span of the legs or any curvature in the part being teste~ can cause a coating to tear. U.S. Patent Numbers 3,628,378 and 3,577,775 disclose apparatus of sim~lar operation.

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Summary Of The_Inventlon The present inve~tion provides an apparatus and me-thod - for tensile adhesion testing o a coatiny to a substrate in which a force perpendicular to the tested material can ~e applied regardless of orientation, curvature or lrregular-ities oE the surface o the testecl objectO
In accordance with the present invention, an apparatus for measuring and testing of adhesi~e bonding of a coating to a substrate in a tenslle mode comprises a dolly having an axially centered opening pass:lng therethrough. The dolly f~rther includes a bonding surface which ~ubstantially conforms to the surface of the coating to be tesked. Bonding means for adhering the dolly bonding surfa~e to the surface of the coating is provided, the bonding means having an adhesive bond strength in excess of the strength of the adhesive bond between the coatiny and the substrate. Also provided are ram means passing through the axially centerecl opening of the dolly, the ram means ~dapted for engagement against a centered portion of the coating surface which is bonded to the dolly~ Piston means are attached to one of the ram and the dolly and cylinder means are attached to the other of the ram and the dolly for forcing the ram into pressure abut~ent again~t the coating surace and placing the dolly, the bondiny l~leans and the coating in tension.
Further in accordance with the invention, the afore-mentioned piston and cylinder means are hydraulically pressurizedO
Still further in accordance with the invention, a method of testing the adhesive bond strength of a coating to a substrate in a tensile mode comprises providing a dolly having an axially centered opening therethrough and bonding the dolly to the coating with bonding agent having a bond strength in excess of the strength of the adhesive bond between the coatiny and the substrate. ~he coating is then cut through to the substrate around the outer circumference of the dolly so that only that portion of the coating bonded to the dolly ; will be tested. The dolly is then attached to piston and , ~
:., ., ~ '' ' ` :
~, ', cyl.inder means which includes an axially centered ram, then passing through the axial opening of the dolly. Pressure is then applied to the piston and cylinder means to force khe ram into pressure engagement with the coating and the pressure is mo~i.tored to the point at which the coating separates from the substrate.
It is ~herefore an object of this invention to provide : a coating adhesion testing method and apparatus for measuring and testing the adhesive bond strength of a coating to a substrate in a tensile mode~ the tension forc~ being applied perpendicularly to the coating surface.
It is another object of this invention to provide an easily portable apparatus for the testing of coating adhesion to a substrate.
; 15 It is yet another object of this invention to provide a coating adhesion tester which may be easily adapted for use :~ on a multiplicity of shaped structures.
Brief Description Of The Drawings : These and other objects of the invention will become apparent through a more detailed desaription of the invention and with reference to the accompanying drawings forming a part of this specification and in which:
Figure 1 is a schematic, cross-~ectional view of the adhesion tester in accordance with the present inv~ntion;
:; 25 Figure 2 is a per~pecti~e view of a dolly used in a .~ preferred form of the apparatus o~ the present invention, ~ and ~ Figure 3 shows an alternative form of dolly in the testing mode of the present invention.
De~ailed Description Of The Preferred Embodiments_and Drawin~s :
~:~ Referring now to the drawings wherein the showings are ~: presented for the purposes of illus-trating a preferred embodiment of the invention only and not for the purpose of limiting same, Figure 1 shows an adhesion tester 10 in position for testing the adhesive bond between a coating 12 and a substrate 14. It will be understood that the coating 12 may be any type of coating such as a paint, a plastic .
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laminate, or a me-tal coating applied by ~ny of sevaral processes such as flame ~praying, electroplatirlg, and the like. Similarly, the substrate~l4 may be wood, a polymeric material, or metal~ For purposes of illustrating a preferred embodiment, the coat.ing 12 comprises a flame sprayed aluminum coating on a substra~e 14 of steel.
In accordance with the invention, a dolly 16 ha~ing an axially centered bore 18 and a bonding ace 20 (Fiy. 2) is provided. The dolly 16 is bonded on its bonding face 20 to the coating 12 with bonding means such as a layer of cured epoxy or cyanoacrylate resin 22 extending between the surface of the coating 12 and the bonding face 20 of the dolly 16.
Although the bonding means 22 i~ preferred to be an epo~y or cyanoacrylate for metal-on-metal coAtings~ any type of lS adhesive material may be used, the criteria for selection of a bonding means being that the a~heslve strength of the bonding means 22 between both the coating 12 and the bonding face 20 of the dolly 16 exceed8 the adhesive bond strength of the coating 12 to the 6ubstrate 14 o As shown in the figures, the dolly is preferably cylindrical in form. It will be understood, howe~er, that practice may dictate other forms which may be used so long as the bore 18 is axially centered in the dolly.
After the dolly 16 has been securely bonded to the coatlng 12, the dolly is attached to the tester assembly 24.
A portion of the tester a~sembly 24 includes a cylindrical inner surface 26 and a cap 28 defining a piston chamber 30.
pisto~ 32 is disposed within the piston chamber 30 and has an axially cente:red ram 34 attached thereto and extending outwardly of the tester assembly 24 through the axially centered opening 18 of the dolly 16 when mounted on the dolly.
In order to separate the tested portion of the coating located immediately under the bonding face 2~ o the dolly 16 from the remainder of the coating which could affect the tensional force required to pull the tested portion of the coating away from the substrate, the coating 12 is scored or cut around the outer circumference of the dolly 16. Any type of cuttlng :,: , , : : -.

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means may be used for -this purpose. This leaves the dolly 16 attached to a ri~g of coa~ing of a known area suitable for quantative ~esting. ~ecau~e of the polnted style of the ram 34, it ls unneces~ary to cut the inner circumference of the bore 18 of the doLly 16 in order to defi~e the coating test area.
Pressurized fluid is adm.itted to the piston chamber 30 through a conduit 36 which is attached to some type of fluid pressurizing means (not shown) such as a hydraulic pump, an air pump, a pressurized fluid reservoir or the like. Various other features may be provided in the tester assembly 24 such as a bleed-off valve 3g for relieving pressure within the piston chamber 30 a~ well as various vent passages 40 for relieving pressure within the c~linder 26 on the ~ide of the piston 32 opposite the pi~ton chamber 30. Bump stops 42 may also be pro~ided to limit the travel of the piston 32 and the ram 34.
In operation of the testing apparatus to test the ~ tensile bond strength of the coating 12 through the substrate ; 20 14, pressurized fluid is admitted to the piston chamber 30 and the pxessure is monitored by any common means. The pressure within the piston chamber 30 drives the piston 32 and its attached ram 3~} into engagement with the surface oE
the coating 12~ An increase in fluid pressure thus causes a tensional force to be developed in the dolly and, thereby, in the bonding means 22 and in the coati.ng 12 as well.
- Because of the axially centered configuration of the ram 34 within the dolly 16, such tensional forces are consistantly applied perpendicular to the ~urface of the coating 12. At the point at which the tension forces in the dolly 16 the bonding means 22 and the coating 12 cause separation of the coating 12 from the substrate 14, the pres~ure monitored within the piston chamber 30 can be used to calculate the adhesive bond strength of the coating 12 to the sub~trate 14 which caused it to fail.

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Figure 3 illustrates an alternative form of dolly 116 which has a bonding face 120 which is curved to conform to the shape o-E the surface of a cylindrical member rather than a planar member as shown in the previous figures. The dolly 116 is bonded to the surface of a coating 112 on a substrate 114 utiliziny bonding means 122 which may be an~ type as previously described with respect to the earlier figures.
The dolly 116 has an axially centered bore 118 shown in phantom for accepting the ram 34 of the tester assembly 24 as previously described. It can be clearly seen that the axially centered nature of the ram 3~ within the central bore 118 of the dolly 116 will cause the development of a ~; perpendicular tensional force to test the adhesion of the coating 112 to the substrate 114.
EXAMPL~
The apparatus shown in Fiyures 1 and 2 was utilized to test the coating adhesion of a flame sprayed aluminum coating applied to a steel ~ubstxate. The dolly face had a surface area of 0.75 inch. The do]ly was bonded to -the surface of the flame sprayed aluminum coating using a cyano-acrylate adhesive designated CA-5 sold by 3M Company. The bond was allowed to cure for 24 hours although 80% of the bond strength may be reached after 1 to 2 hours. The CA-5 adhesive is rated at a tensile strength of up to 5,000 psi.
After cutting of the coating to conform with the bonding face of the dolly, the coating testing apparatus was attached to the dolly and the pressure in the piston chamber was increased until a gauge pressure of 380 psi was noted at which point the bond between the coating and the substrate failed. Based on the size of the piston and surface area of the dolly, the calculated tensile loading and thus the coating adhesion strength at failure was 1,421 psi.
While the invention haq been described in more limited aspects of the preferred embodiment thereof, other embodiments have been suggested and still others will occur to those skilled in the art upon the reading and understanding of the .

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foregoing specification. It is intended that all such embodlments be lncluded within the scope of thi~ invention as limited or~ly by the appended claims.

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Claims (10)

Having thus described our invention, we claim:
1. An apparatus for measuring and testing of adhesive bonding strength of a coating to a substrate in a tensile mode comprising a dolly having an axially centered opening passing therethrough, said dolly having a bonding surface conforming to a surface of said coating; bonding means for adhering said dolly bonding surface to said coating surface, said bonding means having an adhesive bond strength in excess of the strength of said adhesive bond between said coating and said substrate; ram means passing through said axially centered opening in said dolly, said ram means adapted for engagement against a centered portion of said coating surface bonded to said dolly and piston means attached to one of said ram and said dolly and cylinder means attached to the other of said ram and said dolly for forcing said ram into pressure abutment against said coating surface and for placing said dolly, said bonding means and said coating in tension.
2. The apparatus as set forth in Claim 1 wherein said dolly is cylindrical in form.
3. The apparatus as set forth in Claim 1 further including a gauge for measuring pressure between said piston means and said cylinder means.
4. The apparatus as set forth in Claim 3 further including means for providing hydraulic pressure to said piston and cylinder means.
5. The apparatus as set forth in Claim 3 further including gas compressor means for providing compressed gas to said piston and cylinder means.
6. The apparatus as set forth in Claim 1 wherein said bonding means is an epoxy resin.
7. The apparatus as set forth in Claim 1 wherein said bonding means is a cyanoacrylate resin.
8. The apparatus as set forth in Claim 1 wherein said bonding surface of said dolly is planar in form.
9. The apparatus as set forth in Claim 1 wherein said bonding surface of said dolly is curved to conform with a curvature of a cylindrical-shaped substrate having said coating thereon.
10. A method of testing an adhesive bond of a coating to a substrate in a tensile mode comprising the steps of providing a dolly having an axially centered opening therethrough;
bonding the dolly to the coating with bonding means having a bond strength in excess of the adhesive bond between the coating and the substrate; cutting the coating circumferentially around the dolly; attaching piston and cylinder means to the dolly, the piston and cylinder means including an axially centered ram, the ram passing through the axially centered opening of the dolly; applying pressure to the piston and cylinder means to force the ram into pressure engagement with the coating; increasing the pressure to a point at which the coating separates from the substrate and monitoring the pressure throughout the step of increasing the pressure.
CA000508119A 1986-05-01 1986-05-01 Apparatus and method for adhesive testing of coatings Expired CA1272395A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000508119A CA1272395A (en) 1986-05-01 1986-05-01 Apparatus and method for adhesive testing of coatings

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000508119A CA1272395A (en) 1986-05-01 1986-05-01 Apparatus and method for adhesive testing of coatings

Publications (1)

Publication Number Publication Date
CA1272395A true CA1272395A (en) 1990-08-07

Family

ID=4133026

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000508119A Expired CA1272395A (en) 1986-05-01 1986-05-01 Apparatus and method for adhesive testing of coatings

Country Status (1)

Country Link
CA (1) CA1272395A (en)

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