As the thickness and its uniformity of the coated film are very important factors in the case of sprayed zinc coatings in order to protect iron from rusting, We made some measurements of thickness with the“Kaken”magnetic thickness gage and disscussed about the uniformity.
That is, about several samples, thickness measurements were carried out on the whole surface of the coatings from point to point with nearly equal interval, and mean thickness x and un-uniformity p defined by the following relations were calculated,
x=1/NΣNi=1x
i……(1)
p=0.6745/x√1/N-1ΣNi=1(x
i-x)
2-(x×0.05/0.6745)
2×100…(2)
Where x
i is the thickness of the film measured at the i-th point and N is the total numbers of points measured.
As conclusions it was found that.
(i) x is increased nearly proportional to the metal used for spraying.
(ii) p is increased generally as the x is increased.
(iii) p of the coatings prepared by hand-working is much greater than that of the coating prepared by mechanical spray device.
Some topographs of the thickness distribution are shown. From these graphs, it is possible to suggest the trucks of spray and e. t. c.
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