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 Restore metallic part with metal deposit

Metal parts with damage, wear, corrosion or machining defect can be restored to original size using metal deposit method. This will be especially great to save discontinued parts.

Two different types of metal deposit exists :
  - first is to apply new layer of metal by welding. In such case metal is the same of base metal or very similar. In some cases it is also even possible to fit harder material especially for wear resistance purpose. But disadvantage is that welding induce heavy amount of material added needing part machining to retreive shape and welding can distord or soften part due to heavy heat.

 - second process is to apply an thin layer of metal by electrolysis. In this case metal used will be diferent than base metal. Generally chrome is used in insutrial process. This technique will be mainly used to retreive axles diameter in case of wear or corrosion or increase tightening of a bearing in a bore for example. Unfortunately due to difficulty of chroming process and to fing raw material and product this cannot be done at home. But it is possible to replace chrome by zinc which has the double advantage to be easy to machine even with hand powered tools and will also procure protection against corrosion for steel parts. Disadvantage will be that zinc is much softer that metals as steel or chrome so it will limit use to area no submitted to heavy wear. It will also not compensate strength or the part loosed due original defect.

Basically process is the same as described in DIY metal galvanizing method, but it will be repeated several time to obtain sufficient thickness to compensate the defects.
In under pics process was satisfactorily applied to a hand operated water pump axle that was showing heavy corrosion leading to leaks.

For a good adhesion first action is to ensure that part is free from corrosion, it can be eliminated depending of the amount by mechanical means has grinding or sanding but in all cases it will be necessary to finish process by and acid attack (Hydrochloric acid on steel) to ensure that all traces are removed.

Original axle condition :

Then several zinc layers will be applied by galvanizing process in order to compensate defect depth. Result will be better if done in several steps compare to trying to do it in one time. Moreover it will allow you to check thickness and between each bath you can remove excess of material in location not needing  deposit (for example you can remove excess of zing by smoothly sanding not concerned areas) it will ease final step to retrieve original part shape and size. Area not needing repair can also be masked with adhesive tape to prevent deposit of metal.

After galvanizing :

Once you have obtained a sufficient deposit, last step consist to machine part to remove excess of material. For axle the ideal will be to use a lathe but if not available it can be done using a file and sand paper with caution and time.

Axle after final machining (manuallly) :

 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

 10 different ways to loosen a seized screw

Sometimes old screws are very difficult to loosen and force it will damage the head, rending wrench or screw driver ineffective.
Below you will find main methods that can be used to save situation.

1) penetrating oil :
Using penetrating oil in aerosol can afford soothen dirt and corrosion but also to lubricate assembly lowering the unscrewing effort.
Let time to oil to be effective and repeat application if necessary.

2) Pliers :
if screw head is damaged you can try to grasp the head with a clam. Preferably use a locking clip to get a better grip.

3) Impact screwdriver :
its very simple use will loosen screw by simply hitting the screwdriver with a hammer.

4) machine a new slot :
when the head is too damaged you can machine a new slot with a saw or a mini drill equipped with a cutting disc. New slot will allow use of a flat screwdriver. (Press strongly on the screwdriver and help rotation using a pliers on the blade).

5) Special paste :
you can find special paste which should prevent screwdriver to rip. Having not tested yet we cannot state on effectiveness.

6) Heating screw with a torch :
Heat will help loosening by dilatation effect. This old technique is very efficient for rusted screws. The only restriction is if wood or plastic is near assembly, do not reuse screw as heat will have reduced its charateristics.

7) Use a chisel :
Hitting sidewards screw with a chisel will first make a notch and then repetitive hits will start to loosen it.

8) Stud / screw extractor :
First drill a hole in screw. Hole is the key point of this method, it must be well centered and strait. Stud extractor and hole diameter will be selected in accordance with screw size. Then extractor will be inserted in the hole, the rotation (counterclock) effect will force it to enter in the screw and transmit rotation effort to the screw.
Beware that small stud extractors are very fragile if too much or torsionnal effort is applied on it.

9) Weld a nut :
You can weld a new nut on the screw, this will allow you to find a good grip for your wrench. Moreover it will also combine the heat effect (method 6). But be carefull not to weld screw to support at same time or it will be worst.

10) Ultimate method : destroy the screw :
if no other mean was succesfull you can either drill the screw or grind the head. Removal of the assembly will be possible but theaded part of the screw can remain inside thread and can be difficult to extract. There is also a lot of chance to damage the threaded part.

Screwdriver's :

- Before trying to unscrew any old screw take time to apply a dose of penetrating oil that can save you many disappointments.
- Prefer closed wreches to fork type
- Use preferably torx or hex screw types that can bear higher torque and are less likely to damage at unscrewing.