Fire cement stains

[Arnold9801]

Has anyone been able to remove the chalky like stains from their fire and/or their flue pipes?

I’ve been sealing my flue joints with black fire cement and the parts that had fire cement on them, now have a white chalked type stain that won’t go.

Any advice on removing these stains would be appreciated!

Regards

 

[MikeG.]

I've no experience of this at all, but the two standard treatments for mortar stains are "brick acid" and oxalic acid. The latter is more a bleach than an acid, but both should be used with caution, and all the necessary health 'n safety gear.

 

[Arnold9801]

I will try the brick acid, but although this may sound crazy, someone has just told me about “Monster” energy drink! I’ve now looked on the web and there are lots 9f vids on this drink as a stain and excellent rust remover.

Any other ideas and advice would still be welcomed.

 

[Woody2Shoes]

Assuming that fire cement is some kind of cementitious carbonate-based substance, "limescale" by another name perhaps, then the best thing to try is brick acid - per Mike's suggestion above - which is basically dilute Hydrochloric Acid. Most toilet cleaners - with limescale remover - contain a similar concentration of HCl (best to check the label carefully) . Do use rubber gloves and eye protection, making sure to protect other surfaces (esp. wood, paint etc.). Obviously try on a tiny test area first. Cheers, W2S

 

[Arnold9801]

I have used the very popular “Kos” fire cement. This must catch quite a few people out because in having not used it before, I was unaware of the effect it has even if a trace of it is left on the flue pipes. I’m using black flue pipes and black fire cement, but the distinct chalky stains on the black really show up. It appears impossible to get them off, but I will try the brick acid next.

Despite raining Kos technical dept yestrday but not even they had a solution!

Thanks again for those that have replied.

 

[MikeG.]

Assuming that fire cement is some kind of cementitious carbonate-based substance, "limescale" by another name perhaps, then the best thing to try is brick acid - per Mike's suggestion above - which is basically dilute Hydrochloric Acid. Most toilet cleaners - with limescale remover - contain a similar concentration of HCl (best to check the label carefully) . Do use rubber gloves and eye protection, making sure to protect other surfaces (esp. wood, paint etc.). Obviously try on a tiny test area first. Cheers, W2S

The downside of toilet cleaners is that they also generally contain a colour, which might cause more problems than they solve! I think the propriety brick acids are more concentrated than toilet cleaners, too.

 

[Joe77]

WD40 works a treat, use sparingly as is highly flammable’ there will be a slight odour until it burns off. It will remove all fire cement stains

 

[MARK.B.]

Just a thought if you cannot remove the stains by any of the above methods ,have you considered using stove spray paint to cover the stains ? I resprayed the wood burner in the lounge a few years ago and it works really well ,heat resistant to around 650 degrees which is much higher than your flue should ever get. Or get a tube of Black leading and apply a couple of coats then buff with a soft rag , i can remember my Nan using the stuff back in the early 60's to keep the range looking like new.