Quality inspection of passivation of stainless steel pickling - blue feature sta - Chinese Spring Net
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Quality inspection of passivation of stainless steel pickling - blue feature sta
From;    Author:Stand originally
Blue dot experiment is to examine the method of quality of passivation of pickling of stainless steel surface, its principle is to detect whether does stainless steel surface have iron ion to pollute. Iron ion forms galvanic cell in stainless steel surface, can make electrochemistry of stainless steel happening is corroded.
Blue dot examines specific means is: With 1 gram K3[Fe(CN6)] of iron potassium cyanide adds 3 milliliter (HNO3 of 65%~85%) nitric acid and 100 milliliter water make up solution (appropriate is used now match now) . After using solution of filter paper macerate next, stick add at waiting for to measure the surface or measure solution besmear, drop the surface at waiting for directly, the observation inside 30 seconds shows blue dot case, blue dot is unqualified, it is qualification without blue dot. This experiment needs to wait for pickling passivation undertake after the surface is basic and dry.
Film of passivation of stainless steel surface is not perfected or iron ion is polluted, the iron ion that can have free exists, can produce following reaction so: Blue-black 2K of 2Fe K[Fe(CN6)]=KFe[Fe(CN6)] ↓
Blue dot inspection applies at container of stainless steel chemical industry to make commonly, this is law of a kind of very strict check proved recipe, pass to make examine, must abide by procedure strictly, we suggest:
1. stainless steel is placed should have appropriative place, must spread board or oak rubber, forbidden mix with carbolic steel put;
Facilities of 2. of all kinds treatment, if roll trigger, plane shear stage to wait,want to undertake cleaning handling, roller, press horn to want besmear to brush varnish, steel of guarantee against rust is not contacted directly with carbolic steel;
3. tool clamping apparatus uses stainless steel material or gasket stainless steel;
The steel wire of 4. pickling is brushed should pledge with stainless steel material steel wire is brushed;
This method consults standard HG 20584-1998.

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