Adhesion tests scratch

Adhesion test, scratch An adhesion test whereby a loaded stylus with a specific tip configuration is pulled across the film surface under increasing load. The scratched surface is then observed visually for flaking and deadhesion and is correlated to the load at that point. During scratching, Acoustic emission may also be monitored. 

For the balanced beam-scrape adhesion test, ASTM-2197, weights were added to a commercial balanced beam tester. The kind of scratch produced by the stylus with the different loadings was recorded and served as a measure of film hardness. Coatings which are not scratched to bare metal by 500 g are desirable. 

Epoxy acrylate (Ebecryl 3700, 50%) combined with 25% TMPTA, 25% I BOA and with DIBF-OPPI-DIDMA pigment and FC-171 as above was also used to coat panels. These panels showed no removal of coating in the cross hatch adhesion test. With 6.8j there was no loosened coating on the frontal impact surface, and only 30% was loosened on the back surface. Five hundred grams were required to scratch to bare metal with the balanced beam. Performance was... 

Other models were developed by Laugier (1986) Burnett and Rickerby (1987) Bull (1991) and Ollivier and Matthews (1994). For a standard procedure to perform and evaluate scratch adhesion testing, see ASTM C1624-05 designation (Table 7.4). 

Bull, S.J. (1991) Failure modes in scratch adhesion testing. Surf. Coat. Technol., 50, 25-32. 

J. Oroshnik and J. W. Croll, Thin film adhesion testing by the scratch method, Surface Science Symp., New Mexico Section, Am. Vac. Soc., Albuquerque, NM, April 22, 1970. 

There are numerous techniques known for adhesion and delamination testing, some of the most common being a tape test, stud-pull test, scratch test, and an indentation test [1]. In the tape test, a tape is pulled off the surface containing a scratch, which provides the failure initiation. In the stud pull test, a stud held with thermosetting epoxy is pulled off the film surface. The indentation test, wherein a ball is pressed into the surface, is used for hard coatings, and the failure pattern indicates acceptable behavior. In the scratch test, where an indenter moves in both vertical (loading) and horizontal (sliding) directions, an acoustic emission sensor allows for detection of the initiation of fiacture, while the scratch pattern indicates the type of failure. 

The Universal Nano-i-Micro Materials Tester (UNMT) has been developed to perform a variety of the common adhesion tests [2]. During any of them, it can simultaneously measure contact or surface electrical resistance displacement, deformation, or depth of penetration contact acoustic emission temperature forces in all three directions and digital video of the contact area. This report covers evaluation of the adhesion and delamination properties of coatings by the scratch test. 

Specimens in a wide variety of shapes and dimensions (up to 200 mm) can be accommodated. For scratch-adhesion tests, various tool geometries and materials can be used, metal or ceramic ball or needle, diamond stylus or patented micro-blade. 

The multi-sensing technologj-, based on simultaneous high-resolution force and electrical and acoustic measurements, allows for ver> accurate determination of both delamination/ adhesion and scratch resistance of both thin and thick coatings. Using the test tools with higher contact area (or length), like micro-blade or ball, may allow for more repeatable results than those obtained with sharp styluses. 

The scratch tests are very similar to the nanoindentation tests and can be considered side by side. In both teclmiques, a prime tip is used for the adhesion measurements by dragging across the measuring surface under an increasing load, which results in an indentation. Scratch and indentation tests are suitable for the analyses of the coatings and thin films [100]. Sharp diamond indenters are usually used for the adhesion and scratch resistance determination between the substrate and coating. These techniques can fail for the analyses of hard coatings on soft substrates due to no detectable failures as a result of small critical loads. Therefore,... 

W. Heinke, A. Leyland, A. Matthews, G. Berg, C. Friedrich and E. Broszeit, Evaluation of PVD nitride coatings, using impact, scratch and Rockwell C adhesion tests. Thin Solid Films 1995, 270, 431-438. 

Adhesion tests vary considerably depending on the type of coating being tested. By and large, the cellophane tape test is quite common, wherein a piece of adhesive cellophane tape is pressed on an area of the coating which had been scratched, scored or otherwise cut with a sharp edge. 

A simple form of the scratch test is used for assessing paint adhesion (see Paint constitution and adhesion). The scratch test, as described in this article, is perhaps best regarded as a useful comparative method of characterizing thin film adhesion. The test variables used should be carefully characterized and caution exercised in comparing results obtained in different laboratories. 

Arco microknife Instrument designed for testing scratch hardness and adhesion of coatings. A diamond point is weighted until it can penetrate a film to the metal substrate in two retracing steps. The weight necessary to achieve this cutting force for films of standard thickness is a measure of hardness. 

Bull, S.J., Rickerby, D.S., Matthews, A., Leyland, A., Pace, A.R., Valli, J., 1988. The use of scratch adhesion testing for the determination of interfacial adhesion — the importance of frictional drag. Surf. Coat. Technol. 36, 503—517. 

Burnett, P.J., Rickerby, D.S., 1988. The scratch adhesion test an elastic-plastic indentation analysis. Thin Solid Films 157, 233—254. 

A common mode of coating failure is delamination at the coating-substrate interface. The strength of this interface is measured using adhesion tests that range from the simple adhesion scratch test to the more sophisticated tests based on fracture and/or contact mechanics. Many of the qualitative tests, such as the Adhesion Tape Test, are covered in the ASTM standards (e.g. [43-45]). These should be used only for comparative purposes, where a quick evaluation of adhesion is required. 

Chandrasekhar et al. [934] used several independent methods to monitor corrosion, including Tafel Scan, Cyclic Polarization and Polarization Resistance among electrochemical methods Immersion methods Salt Spray Fog techniques vide ASTM B-117-94 and MIL-C-5541E scratch tests and adhesion tests. They found that their coatings had excellent adhesion, passing the ASTM tests mentioned above, and excellent durability in salty atmospheres, as evidenced by the samples differing very little in appearance before and after the Salt Spray Fog tests. 

In addition to standard adhesion tests or failure tests that are explained in the previous chapters of this handbook, various types of special tests are also performed for specific purposes in industry or in scientific research. In this chapter, some special mechanical tests are treated, such as blister tests for membrane/adhesive/coating, tensile tests and shear tests for sealants and elastomeric/foam adhesives, and indentation tests and scratch tests for characterizing coating adhesion. Most of these are designed for testing macroscopic specimens in a macroscopic scale, but several micro- or nanometric test methods have recently been developed to measure mechanical properties of small specimens in a microscopic or nanometric scale. This chapter also introduces recently developed microscopic methods. 

However, the scratch test is one of the most popular adhesion tests in both industry and academic research. This comes fi om the fact that this technique is applicable to the evaluation of a wide range of systems, and commercial equipment is available to perform a variety of functions, such as surface roughness measurement, the evaluation of mechanical properties of the coating, and so on. In particular, the scratch test appears the best technique for most situations for the case of hard and brittle coating. For softer coating, though this test is difficult to extract a true delamination mode fi om, it is still usefiil as a complementary test of other techniques. 

This chapter gives a brief description of special mechanical tests for various types of material and sample geometries, such as blister tests, tensile tests, and shear tests for sealants/foam adhesives, indentation tests, scratch tests, tack tests, and tests for the evaluation of residual stresses. 

Surface indentation using a loaded point can be used for adhesion testing in much the same way as the scratch test. Indentations are made with varying load and tip geometries and the area around the indentation is observed for fracture, flaking, and deadhesion of the film from the substrate.An instrument that can be used for performing this test is the common indentation hardness tester. 

The blister adhesion test (see Figure 11.6) is used to measure the adhesion of coatings and applied films. This is a nontrivial task when it is considered that it is often impossible to grab the coating and pull it from the substrate. Other methods to measure adhesion of coatings are scratch tests and indentation tests. 

Burnett and Rickerby [78] and Bull and Rickerby [79] analyzed the scratch test of a coated sample and derived a relation between the critical normal load Wcr and the work of adhesion... 

Figure 3 presents results of adhesion for LBG1025/PVDF composites. As one can see, in the particular testing conditions, LBG1025 has a poor adhesion (100% of the coating has been removed by the Scotch tape even without a need to make cross-cut scratches on the surface of current collector). 

Test Procedures. Coatings were tested by the following procedures. For crosshatch adhesion, ASTM-D3359, a special scribe was employed which had 11 sharp points spaced approximately 1 mm apart. The film was scored twice with this tool so that scratches were perpendicular. Special tape was then placed firmly over the scored area and pulled off. The number of squares of film coating remaining were counted, and this provided a numerical basis for measuring surface adhesion. No squares are removed for a satisfactory coating. 

Knife test (KNF) The test is done by making two intersecting scratches through the paint film to the substrate with a sharp steel knife. Adhesive or cohesive failures are evaluated by peeling the coating from the intersection point and outwards. Common for the three adhesion evaluation methods are that the test is performed on immersed and non- immersed panel-half (referred to as respectively "wet" and "dry" adhesion). The type of rupture is reported, and the severity is judged on a scale from 5 (perfect) to 0 (poor). 

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