A common fault phenomenon and analysis in the process of plating nickel

Pinhole, pitting and peeling

Plating pinhole, pitting and peeling is the most common fault in electroplating, mainly caused by the following reasons.

(1) the improper heat treatment technology

In the process of mechanical processing, parts surface adhesion of the antirust oil, cutting fluid, machine oil, grease, grinding fluid, demoulding agent, grinding dust and dust mixed together, form a thick dirt. Jorge processing prior to remove more than dirt, the quenching burn up stubborn degreasing derusting difficult to clean after solid oil dirties, shi bubbles when plating adhesion coating formation gas retention type pinhole.

(2) the bad treatment before plating

Surface heat treatment will inevitably adhesive layer of oil, when the dust settled on the surface, with oils and mixed together, time is long it is hard to clean, so that the small oil spot in workpiece surface is not obvious, when plating bubble stranded on the formation pore. Besides using mesh belt type resistance furnace quenching, the impurities such as oil and dirt particles on the surface of the workpiece to mix together, burn up stubborn dirties, solid nitrate tempering, the above oil dirties and nitro salt formation stubborn hot polymer, is difficult to above the dirt thoroughly cleanse, plating hydrogen bubble adhesion on dirt easily, it is difficult to discharge, so that the coating produce pinhole and pitting phenomenon, and as the bubbles grow, coating will automatically burst, desquamate phenomenon.

The plating peeling off

There are two main types of such failure may cause, one is the poor adhesion coating and the magnesium substrate, the second is nickel plating layer brittleness is big, small extension.

Jorge improper handling difficult to remove the dirt or plating pretreatment is not complete, dirt inclusions between substrate and coating, coating and the substrate is very poor, the subsequent assembly processing, easy peeling off.

When the ratio of brightener improper or poor quality, the pH is too high, the cathode current density is too large and the solution temperature too low, can cause hydrogen ions in the cathodic reduction, in the state of atomic hydrogen into base metal and plating, decrease the toughness of the matrix metal and plating and produce "phenomenon of hydrogen embrittlement. In addition, when metal impurity in the nickel plating liquid and the breakdown products too much, also can make the coating produce the phenomenon of hydrogen embrittlement.

Corrosion resistance is poor

Due to the high porosity of nickel plating layer, only when the coating thickness more than 25 micron basically has no holes. So thin nickel plating layer cannot be separately used as a protective coating, had better use double nickel and multilayer nickel system.

Hang a green corrosion

After plating the VCF a 385 antirust cutting fluid to seal the plating, after the antirust cutting fluid drying, formed in the product is green.

Within Kong Lou copper

Because of bright nickel plating solution of deep plating ability not as good as the cyanide plating dark copper, bright nickel plating after plating copper coating on the product inner hole position cannot be completely covered, so the product within Kong Lou is copper.