Nickel-tungsten Alloy Plating Mold Analytic Process(b)

1. Pitting
   
Pitting tiny white coating on the black dot defects, various shapes, some obvious and rules, easy to find, relatively good control; a small amount of eye "invisible", only with the instrument checks.
    
Analysis:
    
Trachoma mold matrix, porosity, pitting, etc. caused by poor adhesion; while blasting sand mold adhesion, or poor sandy or sandy been caused by impurities, oil, foreign bodies, dust and other pollution; mold when degreasing adherent emulsion, cleaning and other impurities in the water; dosing caused when using compressed air, water and pipes, tools and environment pollution impurities; bath, activated liquid salt particles were not dissolved acidification of the electrode metal can cause pitting.
    
Said pitting can be seen intuitively, and some thin layer of adhesive material of the mold surface, the analysis is mainly contaminated sandy before plating the carbon-based compound. It is solid, strong adhesion gradually becomes acid alkali, anti-vibration high viscosity gum. In degreasing, cleaning difficult to remove once negligence inflow plating process, must be covered by the coating, the naked eye is not easy to find, can not make up.
   
2. Coating roughness
    
Analysis:
   
Bath consisting essentially of nickel sulfate, sodium citrate, sodium tungstate, etc., as well as salts, organic complexes and the like. It was found: mold plating defects and impurities in the bath main relevant. Not high purity chemicals, foreign body in the bath, the bath is frequently used to make the bath metal impurities Cu, Fe, Cr, Co content exceeds the allowable range, can lead to coating roughness, increased pitting and white particles.
    
3. Severely uneven coating thickness
    
Central and side, the corners, R at the coating serious inequality, and even the corners, R occurring at the micro-cracks.
   
Analysis:
    
After the bath using a longer time, the probability of an increase in the coating defects, side and white spherical particles, the corners, especially at the micro-cracks R evident. It was found: When the bath impurities Cu, Fe, Cr, Co content were significantly increased 20,20,20,50mgl, plating quality decreased.




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