Too long in descaler?

[Brian GParticipant @briang]

A friend put some boiler fittings in diluted Kilrock (formic acid) overnight to remove limescale and remembered them a week later. Unsurprisingly the parts are now bright pink, but we wondered if any damage may have taken place deeper into the metal that could affect their performance?

Thanks for any advice

Brian

[Brian GParticipant @briang]

Formic acid pickle used for descaling

[RJWParticipant @rjw]

Sounds like a similar reaction to brass left in Horolene and similar brass cleaners containing ammonia where the ammonia strips the zinc out of the surface of the metal, if the fittings have been left in the acid for that period, personally I'd bin them and replace.
I've no experience with boiler fittings at all, so other more knowledgeable people may advise differently, but there are cases where a similar reaction with ammonia based cleaners have caused microscopic cracks in the metal and subsequent fatigue failure.

John.

[frank brownParticipant @frankbrown22225]

The acid has dissolved the zinc. I have had marine fitting which went like this and had zero tensile strength. "Honest Guv, it just came off in my hand".

Frank

[Brian GParticipant @briang]

Dezincification was what worried me, although in this case I wasn't sure which metal would dissolve first. Fortunately it looks like a lucky escape as my son just heard back from our friend that the parts involved were all bronze and appear OK.

Thanks

Brian

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian G on 03/11/2015 19:11:42:

… just heard back from our friend that the parts involved were all bronze and appear OK.

.

You probably know this, and I admit that it is a gross simplification, but;

note that Bronze is an alloy of Copper and Tin [whereas Brass is a mix of Copper and Zinc]

MichaelG.

[julian atkinsParticipant @julianatkins58923]

Michael,

that is a bit of a 'cop out'! i was hoping for a full chemical analysis and treatise!

my old friend Jack Poyner who wrote the MAP book on electro plating gave me a bottle of concentrated formic acid for descaling boilers. Jack was a chemical wizard. unfortunately i found the formic acid not that effective on baked on limescale in miniature loco boilers. i never tried it on anything else and still have half a bottle in my shed.

cheers,

julian

Edited By julian atkins on 03/11/2015 22:03:47

[Michael GilliganParticipant @michaelgilligan61133]

Posted by julian atkins on 03/11/2015 22:03:16:

Michael,

that is a bit of a 'cop out'! i was hoping for a full chemical analysis and treatise!

.

Sorry, Julian … You're not going to lure me into even attempting that !!

There are so many variations on the Bronze theme that I wouldn't know where to start.

Apart from the Tin vs Zinc constituent, I believe that the most important difference is that [as I hinted] Brass is a mixture rather than a true alloy, and therefore the Zinc is 'accessible' to chemical attack.

Beyond that, I'm lost.

MichaelG.

[julian atkinsParticipant @julianatkins58923]

Michael,

i am disappointed!

there was a thread on here awhile back re a commercial brass blowdown valve that had badly corroded. my view of same was that the fitting had been overheated when silver soldered as a fabrication. ive had same last 30 years in miniature loco boilers.

citric acid (diluted) will produce the same 'pink' characteristics as Brian described after 3 hours. dezincification is quite discernable as a crystaline effect. this is quite distinctive.

cheers,

julian

[Michael GilliganParticipant @michaelgilligan61133]

Posted by julian atkins on 03/11/2015 23:00:56:

dezincification is quite discernable as a crystaline effect. this is quite distinctive.

.

… because, in Brass [especially in cast Brass] the Zinc is in 'macro' size and its removal [by evaporation, or by chemical attack] leaves visible crevices and holes.

MichaelG.

[jason udallParticipant @jasonudall57142]

Wasn’t aware of the macro/nano difference .

Brass can be supplied in very “tight” recipe. .and similarly in very loose recipe.

As can many other materials used…
For example bronze. .

These “alloy”..to some extent are just mixtures.

Tin/lead solder for instance is called a eutectic mix ( ironically more an alloy than mix )..where does this leavw us?

Well there is a reason why certain fittings/parts are specified in bronze rather than brass…
If nothing else tin is much less reactive than zinc ..and would not fizz away and leave the amorphous copper stranded.
Btw alibronze..anyone?

[OuBallieParticipant @ouballie]

MichaelG,

Now that you've made a start on that treatise, please continue

Geoff – Waiting in anticipation

[Michael GilliganParticipant @michaelgilligan61133]

Posted by OuBallie on 04/11/2015 08:44:30:

Geoff – Waiting in anticipation

.

Will this get me off the hook for a while, Geoff ?

MichaelG.

.

Edit: This page might be more relevant to the present discussion.

P.S. … Here is another useful reference.

Edited By Michael Gilligan on 04/11/2015 08:58:45

Edited By Michael Gilligan on 04/11/2015 09:09:55

[Author]

Posts