Citric soak

[A. G. Maisey]

Thanks Giovanni.

If it also removes the rust that is underneath the gold, then that would trouble me, because with old kinatah it is only the rust that is holding the kinatah in place. With kinatah we need to remove the surrounding rust and not disturb what is under the kinatah.

I do think this electric method might be better for a plain steel blade though.

[drdavid]

Hi Gio
what strength NaOH have you used in this set up
what sort of wire are you using in the coils, copper?
regards
DrDavid

[Gavin Nugent]

Thank you all for an interesting insight.

Soaks and such have been noted throughout various threads that they take better with heat...is this true of the citric soaking? With some steel and specialist chemicals I have personally seen some benefit in this but I ask also for economy too (saving product)...I am thinking, as the citric soak is not a harsh chemical, of keeping the required pine apple juice or other mix I may make in the fridge, encapsulated in capped PVC tubing for longevity and actually soak blades in the tube in the fridge...just something I have been pondering...does anyone have any experience with such notions?

With thanks

[GIO]

Originally Posted by drdavid

Hi Gio
what strength NaOH have you used in this set up
what sort of wire are you using in the coils, copper?
regards
DrDavid

Hi David
Please apologize for my late answer, but a thunderstorm has put out of order my phone line and burnt my modem. Only this morning all has been repaired,
As to the electric de-rusting, my plant is not exactly what recommended in the book, but it works.
I use a rectangular plastic flower pot, on the floor of which I have put a serpentine of iron wire (about 1,5 mm thick). The quantity of NaOH is 1 - 2 tea cups per 5 litres (I think that the concentration has some influence on the time required for cleaning). The rheostat is needed for starting the reaction with a low voltage, increasing it slowly. I do not have a rheostat and I use a car light bulb to avoid a short circuit. The power comes from a 12 V car battery charger. Obviously the piece to be treated should not touch neither the iron wire. I suspend it with some pieces of plastic.
When the reaction starts, I can eliminate the bulb, and the reaction becomes more violent, but I prefer to leave the bulb in the circuit to avoid any risk, particularly when the system is unattended. Of course the current is lower and time needed is higher.
When the process ends the piece is black and it needs to be brushed to eliminate all the transformed rust.
When I am back home (beginning September) I shall send you the original text (from a French book: "Restauration des armes à feu"). If you have any doubts please feel free to contact me again.

Alan
Yes, I agree with you: any de-rusting treatment is very risky to kinatah if the iron is heavily rusted. If the rust is light and has not yet developed under the gold foil the treatment is safe, but always great attention is needed.

[A. G. Maisey]

Thanks for your additional comment Giovanni.

Where the kinatah work is only gold foil I would be reluctant to touch it with just about anything, even when it looks good and not heavily rusted, but there is also much heavier kinatah work that uses either very heavy gold over an iron carved figure, or heavy carved gold. With this type of work I believe your electric method could be fairly safe with any except the worst of corrosion.

[GIO]

Originally Posted by drdavid

Hi Gio
what strength NaOH have you used in this set up
what sort of wire are you using in the coils, copper?
regards
DrDavid

Hi David,
I have made a free but faithful translation of the original text about electric de-rusting (from "Restauration des armes à feu" by Jean-René Clergeau, Stampfli & Cie, Berne 1981)

Electrolysis
This procedure is based upon the reduction of oxides through direct current.
This is carried out in a container for electrolysis where the piece to be de-rusted is the cathode. It is easy to find the necessary material, the more expensive component is a 6 or 12 V car battery charger. The cylindrical container can be of any insulating material (ceramic or plastic-which is better) of a convenient size. For keris cleaning a height of 70/80 cm and a width of 20 cm can be utilized for any size, including Panjang.
The anode is made with an iron bar, of the type used for concrete, 6-8 mm thick, made up in a spiral against the internal wall of the container. At an end the positive pole is connected, while the negative pole is connected with the piece to be treated through a non-galvanized iron wire. The piece must be fully submersed and should not touch neither the bottom of the container nor the anode. The electrolyte is a solution in water (better rain water-I use distillate water used for batteries) of caustic soda in granules in the proportion of 50 grams per litre. This solution shall be filtered from time to time, and the anode cleaned.
On the positive thread a rheostat should be inserted, so that the electric power can be reduced, mainly for starting the reaction, so that the battery charger is not unnecessarily strained. A buzzer can be useful for indicating a surcharge. The sound will warn to reduce the power, and increase it as soon as the electrolyse process starts , demonstrated by the appearance of hydrogen bubbles (this happens quickly). The operation must be left working for 12 to 24 hours, but a longer period is allowed.
The blade, once the process ends, will show a blackish surface of reduced oxides, which must be eliminated with washing and brushes (of bronze, if necessary), until the metal appears clean and brilliant.
CAUTION: THIS PROCEDURE MUST NOT BE USED FOR SPRINGS WHICH BECAME BRITTLE (luckily our keris do not have springs), AND A GREAT ATTENTION SHOULD BE PAID IN CASE OF KINATAH ON VERY RUSTED BLADES.
The illustration transmitted last month should help.
I hope you will find such information useful

[A. G. Maisey]

Why did the springs become brittle?

Difference between a spring and other ferric material is that the spring has been hardened and then the temper has been drawn.

A weapon is heat-treated in the same way, that is, it has been heat treated and often the temper that it has been drawn to is the same as a spring.

A keris is also heat treated, but with a keris, because of the laminate construction probably only the hardened edges of the core will react in the same way as a spring, ie, they must become brittle.

After reading this I would hesitate to use electric rust removal on any keris except perhaps the old junky corroded ones that have lost any hardened material long ago. I would not use this treatment on any keris that I valued.

[GIO]

[QUOTE=A. G. Maisey]Why did the springs become brittle?

QUOTE]

Good question, Alan
I am not in a position to answer. I only report what is indicated in the book I mentioned.
In my very humble opinion, the heat treatment ("temper") of a keris is far from the procedure needed to harden a spring, both for what the heat needed and for the partial section of the blade which is interested. In fact a keris blade can be easily bent, and this should not happen easily in case the steel iron core is tempered. It is true that also Japanese katanas can be bent, and this could be due to the fact that different types of steel are layered to form the blade, and different percentages of carbon should be differently treated (different temperature of the heating and of the water), and the keris is made in a similar way as the katanas.
Always in my very humble opinion the heat treatment of a keris is intended more to eliminate tensions in the metal due to the hammering than to harden the blade.
I repeat that I know nothing about these matters and should be very grateful if some more prepared friend would contribute and give a competent opinion.

[Emanuel]

Originally Posted by A. G. Maisey

Why did the springs become brittle?

Rust removal through electrolysis is subject to hydrogen embrittlement: http://en.wikipedia.org/wiki/Hydrogen_embrittlement

Hydrogen evolved from the water through the electrolytic process can fuze with the object and induce cracking. Low-alloy, medium/high carbon steels like spring steels are apparently very susceptible to this.

Reversing the hydrogen absorption is done through heating.

There's never any quick solution I guess.

Emanuel

[A. G. Maisey]

Re heat treat.

For simple forge heat treat, the heat treatment of a spring and a blade is the same, the only variation is the colour to which it may be drawn, and even that does not always vary.

In simple terms, after annealing, you heat the object to be hardened to critical, which can be most easily detected by testing with a magnet:- when the magnet does not grip the object it is at critical temperature.

The object, either blade or spring is then plunged into the cooling medium, which may be water, or oil, or brine, dependent upon the steel to be hardened.

After the hardening the temper is drawn. There are a number of various indicators used by traditional blacksmiths to gauge the correct temperature, for a spring, some old timers would run a piece of hardwood down the object and gauge the temperature by the colour and character of the sparks thrown off.

The usual textbook method is to clean off the surface to be drawn, and re-heat the object until the correct colour for intended hardness shows, then cool the object again in the cooling medium.Different levels of hardness are required for different purposes.

As noted, a keris blade, and many other blades, are laminated, and in the case of a keris, only the projecting edges of the blade core are homogenous steel, the laminations that sandwich the core are irons of various qualities, or iron + nickelous material. This is the reason I wrote:-

A keris is also heat treated, but with a keris, because of the laminate construction probably only the hardened edges of the core will react in the same way as a spring, ie, they must become brittle.

The heat treat of a keris blade is not done to relieve any tensions.

The blade would be annealed to relieve tensions, not subjected to a heat-treat to relieve tensions.

However, a keris blade is carved from a forged blank (bakalan):- most of what we see in the blade is produced by stock removal, and during this process the blade may have been returned to the forge several times prior to heat-treat. By the time it actually gets to heat-treat stage there is probably not much, if any, tension to relieve. Put it another way:- I've made a few keris and a whole heap of damascus and plain carbon steel blades. I always annealed the damascus and the carbon steel, I never annealed any of the keris I made.

Some keris blades can be bent, but not necessarily all --- or more precisely, not necessarily all blades can be bent in the hardened section of blade; since hardening of a keris is only for part of the length of the blade, they can all be bent in the unhardened section.

The temper is not drawn in a keris blade, it is simply plunged point first into the cooling medium. End of story. If the laminations are the traditional irons or iron and nickel, yes, you can bend the hardened section of the blade a little without too many concerns, however, if steel has been used as a laminate material it may or may not bend.

In the damascus blades that I made I did not draw the temper in small blades, like trout/bird blades, but in other larger blades that could conceivably be used for chopping I did draw the temper. The reason I did this was because the small blades were intended only to cut, and if the temper was not drawn the edge would last longer, but the bigger blades that might be used to chop could gap if the temper was not drawn, and that edge would not hold as long as the small blade edge.

Emanuel has given us a link to additional information as to exactly why this cracking can occur. I do not fully understand what I've read, but I think it comes down to :- ferric material that is hard is susceptible to cracking. Ferric material that is not hard is not susceptible to cracking. But I am unclear as to whether it is the quality of hardness, or the content of carbon that leads to this susceptibility.

In any case, it seems that an old, degraded keris would be quite safe to de-rust using electricity, but a well preserved good quality keris would be at high risk.

[A. G. Maisey]

It has occurred to me that some of what I have written in the preceding post could be clarified.

The photos are of my desk knife. It is 01 damascus, I made it about 30 years ago --- in fact, it was the first piece of damascus I made, it was intended to be a 10inch bowie, but it was full of faults that I kept on removing until I finished up with a desk knife.

It has been given a spring temper, that is, it was hardened and drawn to a full blue. This means that it is pretty hard, holds an edge very well and will bend and return to dead straight.

The link will take you to a page that explains the colours that we use as a guide for drawing a temper.

http://www.anvilfire.com/article.php...s_hardness.htm