I looked in some of the older topics, but couldn't find this one. It concerns blade etching (for temper lines, not logos). Today I purchased some ferric chloride etchant and trisodium phosphate to neutralize the etchant. I know to dilute the etchant 4 to 1 with water, but I don't know how strong to make my TSP solution. Any help would be appreciated.

I use ammonia straight out of the bottle. It is recommended over TSP in one of Tim McCreight's books.

Brett

I use the TSP as it does a bit of passivating the steel after the Ferric Chloride. I used 1/2 cup to a Qt of water.

Make sure you dilute with distilled water...

I had some problems with tap water contaminating the ferric...

Also I do not use any tsp or ammonia- I scrub the blade with soapy water and #00000 steel wool, buff with tripoli, clean with acetone / alcohol and then oil the blade... I have noticed that Marvel Mystery oil darkens the pattern up a bit. Have not noticed a difference w/o tsp, so I just stopped using it.

It might be that all the scrubbing, polishing, cleaning and oil get rid of any ferric residue anyway.

Mondt- what do you mean by 'passivating,'?

Passivating is a process used in chemical reactors or on metallic surfaces which come in contact with substances which could be reactive to the free ions on the surface. Passivating neutralizes the surface against chemical reaction. For example in pharmaceutical manufacturing most drugs are compounded in glass lined tanks because of the potential for chemical carry over or chemical reaction with a stainless steel tank.

When passivating you wash the metal surface with an agent to chealate (deactivate) the exposed free ion. For example on a non-stainless blade the surface is covered with iron in a matrix of various carbides. Left alone some of the iron will convert to either a +1 or +2 ionic state and react with the most reative chemical around, oxygen. Hence the terms rust, patina, corrosion, oxidation, ect.

There are many different types of passivation agents, ranging from phosphates and citrates to sodium hydroxide and nitric acid. It all depends on the material being treated and what it is coming in contact with.

It seems to me that damascus treated with TSP may be a bit tougher to get rust on. This is just my observation though, I have never put it to the test.

Hope this helps.

Thanks, Mondt...

I've heard of 'neutralizing,' to prevent further etching by left-over acid, but passivating sounds like w hole different game.

I'll have to do some comparative tests with the tsp / no tsp as far as rust goes.... hadn't even considered that one.