Plating
Advantages
and
Disadvantages

Cadmium Plating

 

1. Advantages
    

   1. Corrosion protection; sacrificial coating corrodes before underlying metal substrate

   2. Especially protective in a marine (salt water) environment

   3. Natural lubricity. In fact, the corrosion product, cadmium oxide, is an excellent lubricant! Corrosion products are not voluminous which means that the corrosion products will not jam the fastener and freeze it as you try to remove it. Therefore, cadmium is an excellent choice for threaded assemblies especially if disassembly is contemplated such as during overhaul and repair. Cadmium surfaces do not gall like stainless steel or aluminum surfaces.

   4. Excellent choice for plating fasteners or moving parts

   5. Excellent electrical conductivity and low contact resistance. Noncorrosive fluxes produce top quality soldered joints and connections.

   6. Prevents electro-galvanic corrosion. When you insert a steel fastener into an aluminum body, e.g., an aircraft fuselage, you just created a battery! Dissimilar metals in the presence of a conductor (water condensation) and a bit of salt creates electrical current! Cadmium prevents corrosion in such important applications

   7. Highly ductile; steel coated with cadmium can be formed and shaped

   8. Can be electroplated on malleable iron, cast iron, powdered metals, and other difficult surfaces

   9. Can be joined to other surfaces with adhesives.

   10. Powerful biocide action prevents contamination by barnacles, etc.

Disadvantages
 

1. Toxic! However, if you wish to keep marine organisms from growing on your part or fastener, this is an advantage. Do NOT use it where the coating can contact food for humans or livestock. Care must be taken to keep cadmium out of the environment. Do not breathe the dust from grinding or welding fumes. Special precautions must be taken with employee safety when plating, and rinse water must be evaporated safely.

2. Outgases and sublimes (become a gas) at 650F.

3. Not resistant to many acids and alkalis. Easy to strip!

4. Inefficient plating process leads to hydrogen embrittlement. Baking before and after plating recommended if part is RC32 or above in hardness (145KSI or above tensile). Cannot be used if the parts are RC54 or above because the steel will be brittle before you can even complete the plating process! Above 240KSI, you need Cadmium Fluoborate plating which we also perform.

5. Cannot be used in a vacuum, i.e., on spacecraft. It will sublimate and coat surfaces such as electronics.