Coating thickness

The war itself also drove the development of improved and miniaturised electronic components for creating oscillators and amplifiers and, ultimately, semiconductors, which made practical the electronic systems needed in portable eddy current test instruments. The refinement of those systems continues to the present day and advances continue to be triggered by performance improvements of components and systems. In the same way that today s pocket calculator outperforms the large, hot room full of intercormected thermionic valves that I first saw in the 50 s, so it is with eddy current instrumentation. Today s handheld eddy current inspection instrument is a powerful tool which has the capability needed in a crack detector, corrosion detector, metal sorter, conductivity meter, coating thickness meter and so on. 

The results found for the coating controlled parts allow to consider during the testing the exploitation of the information provided by the measured variation impedance for the processed products by the coating thickness determination and low frequency homogeneity and to evaluate the high frequency coating nature. 

The required resolution for the powder coating thickness measurement problem is about 5 microns. Therefore a processing time unit of 0.08 ps (12.5 MHz) seemed to be ok (compare line 2 in table 1). First results based on real measurement are documented in Fig. 7. and are very promising result. Today corresponding patent is pending [7]. 

Operation and Control. The amount of current appHed to the part determines the speed of which the anodic film is formed. Generally, a current density of 12.9—25.8 m A/cm (12—24 A/ft ) is appHed to produce a coating thickness of 10—20 p.m (0.4—0.8 mils) per 20 minutes. Most coatings range in thickness from 5—50 p.m (0.2—2.0 mils). 

The coating thickness may range from 0.0025 to 0.05 mm, depending on the type of protection required. Pure tin coatings are used on food-processing equipment, milk cans, kitchen implements, electronic and electrical components, fasteners, steel and copper wire, pins, automotive bearings, and pistons. 

However, most coating machines are required to produce many different products and coating thickness and the machine is therefore usually a compromise for several appHcations. Table 1 describes the capabdities of some of the principal coating processes. 

The ends of the knives can be square, beveled, or rounded. If the end is square and parallel to the web, if the upstream face is perpendicular to the web, and if there is a fixed gap between the end of the knife and the web, then the wet coverage is exacfly one-half the gap. On the other hand, if there is a low angle in a converging section of the knife or of the blade, leading up to a tight gap, as there is for many knives and for all bent blades, then strong hydrodynamic forces build up and tend to lift the knife or blade away from the web. This forces more fluid under the knife or blade, so that the coated thickness is greater than half the gap. 

Fig. 4. The effect of blade loading on the wet-coating thickness in flexible blade coating where ( ) represents a less stiff blade (B) represents a stiffer...

Nutrients are released from POLYON-coated fertilizers by osmotic diffusion. The RLC process permits appHcation of ultrathin, hence lower cost, membrane coatings which distinguishes this technology from many other polymer-coated fertilizers. The coating thickness determines the diffusion rate and the duration of release. POLYON-coated urea at a 4% coating (44% N) will release at twice the rate and will have half the duration as an 8% coating... 

B554 recommended practice for measurement of metallic coating thickness on nonmetaUic surfaces... 

A.STM B487, Std. Test Methodfor Measurement of Metaland Oxide Coating Thickness by Microscopical Examination of a Cross Section, American Society for... 

DETERMINATION OF COATINGS THICKNESS BY MEANS OF DESK-TOP XRF SPECTROMETERS... 

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