Tools can be useful to measurement of color at visual supervision with use of digital values. Numerical measurements are usually carried out by means of spectrophotometer or colorimeter which measure the sample and the standard and represent a difference by means of the differential equation on the chosen color. Values of color usually represent in three-dimensional coordinates.
Image sharpness is defined by visual way or by means of special devices.
The factor of contrast characterizes coverings spreading capacity, i.e. ability to hide distinctions in color substrates. The factor of contrast is defined by measurement of covering reflection from the contrast substrate, which is half white, half black. Usually, if the covering on a black site makes 98 % of white site reflection of surface, the covering is considered visually opaque at the given thickness.
Film thickness influences operational qualities of the covering; except for that it defines the material consumption and, accordingly, it is important to control it. Usually to measurement of this parameter on steel apply a magnetic measuring instrument of thickness. Such devices have constant spring loaded magnet and the graduated scale, it shows force which is necessary for putting to separate magnet from a substrate. As this force is connected with thickness of a film, it is possible to judge film thickness under the indications observable on the graduated scale. For substrates from metals, such as aluminum, is used the device working on a principle of vertical currents. There are devices, allowing defining thickness as on magnetic and not magnetic substrates. Film thickness can be determined also by destructive methods with usage of microscope or micrometer.
Durability at impact is a parameter of ability of a covering to maintain shock influences. Impact from a covering is regarded as direct impact, from a substrate - as return impact. Both of methods are used for an estimation of crashworthiness of coverings. At such test by the important factors thickness and elasticity of a substrate are, they should be supervised for reception of reliable results. The most widespread device for measurement of impact is the pile driver which represents load freely falling in a vertical pipe. The anvil is located under the bottom surface of a tube, it supports the falling load. The load falls from various height on head with the ball, forming dredging of different depth on the surface. Results usually express of 1 kg in centimeters of height of falling of load in weight. Specified value represents the maximal impact which has not broken the covering at the certain thickness of film. Film thickness is connected directly with crashworthiness. In process of film thickness increase the resistance of a covering impact decreases.
The Test for flexibility defines ability of covering to resist to a substrate bend. Flexibility is checked by means of rounding a tin plate with a covering around of conic mandrel. The smallest diameter at which does not occur bursting, is value of flexibility for the covering at the certain film thickness. Thus it is possible to measure length of a formed crack at change of mandrels obliquity.
In the device simple cylindrical cores of various diameters can be used also. Tests for a bend mean a dense grasp of a substrate with the covering rendered on it around of a core. Other test for flexibility is spent by means of the device - Erichsen press. The given test is similar to test for return impact; however speed of deformation here is much less, and it is carried out by means of use hydraulic the press, pushing out a ball from a underside of a substrate with a covering. A measured parameter - length of an covering extract before occurrence on it of a crack. Film thickness directly influences flexibility. In process of film thickness increase ability of the covering to be extended decreases. Thick film has smaller values of elasticity at pressing out on Erichsen press, than thin.
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