DIY metal galvanizing
Galvanization is one of the best method to protect steel parts. It consist of a small layer of zinc deposit at the surface of the part that prevent steel to rust.
It is usually applied in industry but you can also make it simply at home for smal parts.
Material :
- sheet metal of zinc
- sulfuric acid (acid used for car battery)
- plastic cup
- cooper wire
- preferably 6V (or 12V) car battery charger
Screwdriver's method :
This process work as an electrolysis, first thing to do is to obtain electrolyte to make the bath.
Ce procédé marche suivant le principe de l'électrolyse, il faut donc commencer par obtenir l'électrolyte :
- cut in small pieces the zinc and put them in a plastic cup (bottom of bottle will be good). Then add with caution the sulfuric acid. Take care as an heavy gaz (hydrogen) rejection will occur and it can become very hot (do this outside). Preferably add the acid in several times by small amount
- wait until no more gaz bubbles are visible. Some zinc may have not be dissolved but the important is to obtain a sort of white salt at the bottom of the cup.
- remove undissolved zinc and add water (preferably demineralized) to dissolve the salt
- filter the solution (coffe filter) to remove impurities
Once this step has been done you can start galvanizing process :
- steel must be very clean, free from grease, paint and rust. To remove rust you can sand part first and then dip it into Hydrochloric acid
- attach part with cooper wire
- attach a piece of zinc to an other cooper wire
- put the part and the zinc into the bath you have previously done. Distance between part anzinc may be adjusted to obtain good results
- too close result may be not homogeneous
- too far time will increase
- connect wires as followst :
- part to neutral - of battery chager
- zinc to positive +
- You will see small gaz production (oxygen and hydrogen). According to part size and current galvanizing time may vary. You can do some test to now exact amount of deposit you have. To ensure protection thickness must be sufficient
- rince part with water to remove bath product
After galvanizing you will obtain non shining gray coloration. You can brush the part with a metallic brush to retreive the specific shiny aspect of industrial galvanised parts.
Bath can be keept for futher use. Anyway do not dispose in toilets or outdoors as it contains pollutants.
Possible defects :
- non homogeneous deposit : part is too close from anode or part is too wide
- put more distance between part and zinc
- excted the surface of zinc or put a second zinc part at the opposite
- surface aspect is not smooth and some peak are visible (peaks especially occurs at angles) :current is too high
- lower the current or voltage (if possible)
- add water to dilute electrolyte
