Specific materials are used for specific processes. For example, the galvanized fingerprint resistant material cannot be used in the electrophoretic process, which will cause the electrophoretic parts to be scrapped. How to quickly identify whether there is a transparent coating on the surface of galvanized materials is a very important skill.
Passivation, fingerprint resistance and other post-treatment methods are to apply colorless and transparent post-treatment film on the galvanized substrate, which is difficult to identify visually. There are many professional detection methods, but finding a low-cost and efficient method is our goal.
Test methods for chemical experiments
1. Principle analysis
The essence of fingerprint or passivation resistant products is to apply an organic coating on a galvanized substrate. Due to the existence of the coating, we can find a chemical reagent that reacts with the zinc layer instead of the coating, and distinguish it according to the difference of reaction speed.
2. Experimental prop – 5% copper sulfate solution
Next, we grandly launch the protagonist of this issue: copper sulfate solution. Of course, if the concentration is not too high, 5% concentration is enough (colorless and transparent).
3. Detection and judgment
The copper sulfate solution will react with the zinc layer (Zn + CuSO4 = ZnSO4 + Cu), as follows:
Drop 5% copper sulfate solution onto the fingerprint resistant or passivation resistant product, and let it stand for 3 minutes, and the solution is still transparent.
Drop on the uncoated galvanized sheet and let it stand for 3 minutes. The solution reacts with the zinc layer and turns black.
matters needing attention
During the actual operation, the plate surface must be wiped clean with alcohol, otherwise the residual antirust oil will also delay the reaction speed.
A bottle of solution, drop by drop, 5 minutes, solve all problems!
Fauvist solutions
The above is the simplest academic solution. The next is the real dry goods. Students who haven’t finished reading can’t enjoy this benefit!
In fact, Chaige himself used a simpler and faster method: finger rubbing method
After the sample plate is wiped clean, use your fingers to vigorously and repeatedly rub on the plate surface (friction, like the devil’s pace ~ ~).
The fingers blackened (with zinc powder falling off) are uncoated galvanized sheets. If there is no obvious change on the surface, it indicates that there is a post-treatment coating.
remarks
This method requires a little experience, but it is cheaper and more versatile. What does the production site need? Fast, simple, rough!!!
Post time: Jun-11-2022