Porosity Tests for Electroless Nickel Deposits

Electroless Nickel Plated parts may be inspected for pits and porosity by a number of methods.

Ferroxyl test.

This test is for use with EN on steel and iron basis metals. Prepare a test solution by mixing 25 grams of potassium ferricyanide and 15 grams of sodium chloride in one liter of deionized water. Clean the article and immerse in test solution for five seconds. Blue spots visible on the surface indicate pore sites.

Copper sulfate test.

This test is also for deposits on iron and steel basis metals. Immerse or swab the deposits for 15 seconds using 60 g/liter copper sulfate acidified to pH 3.0 with sulfuric acid. Pore sites will be indicated by copper-colored spots on the deposit.

Alizarin test.

This test for deposits on aluminum alloys is performed wiping a test specimen with a 10 pct sodium hydroxide solution. After the minutes, rinse and apply the solution of Alizarin sulfonate.
After four minutes, apply glacial acetic acid until the violet color disappen Red spots indicate pore sites. The Alizarin sulfonate solution is prepared dissolving 1.5 grams of methyl cellulose in 90 milliliters of boiling deionization water, to which, after cooling, a solution of 0.1 gram of Alizarin sulfonic are dissolved in five milliliters of ethanol is added.

Hydrochloric spot test.

This test is for deposits on aluminum alloys. It performed by immersing the article which has been plated into a solution 50 pct hydrochloric acid at room temperature for two minutes. Black spots the surface indicate pore sites.