Need help with an acid test

[stewiestew]

I never have done one before. I got some parts that seem gold plated and have an acid test kit but when I apply the acid to the scratched surface it doesnt seem to be right.
I scratched the surface with a screw driver in 4 spots and applied 4 different acids. What do you think is the problem. The parts are from a HP unit from the 80's or 90's.

 

[butcher]

From the description of what you have done (calling it an acid test), and the pictures it appears to be what I would have concluded without using any acids at all.

A thin layer of gold with a scratch exposing base metals with copper.

The acid attacked the base metals, and in this case also dissolved some gold that plates back out onto the base metal...

Because you used aqua regia.

The same test if you suspected base metals under the layer of gold, and could not just see it with your eyes, just using a drop of nitric acid would give similar results without dissolving the gold in the test. The green color of oxidized copper.

There really was no reason for this test as you already knew the part had base metal copper under the gold which you should have recognized after scratching through the thin layer of gold...

My suggestion is to study more about how to test different scrap metals and solutions, learning why the tests are performed on certain materials and in certain ways differently, and how to preform those tests.

 

[g_axelsson]

You are doing it totally wrong. The plating is 24 karat on plated objects.
Acid gold test are meant to test solid gold alloys and you use a touch stone to make a trace of gold and then compares it to a similar streak made with a known alloy.

How to do it correctly... found the link on GRF.
https://link.springer.com/article/10.1007/BF03216559

Göran