Removing hardened Cement from Metal

Apart from the usual chipping and scraping, can anyone suggest a method of removing encrusted cement from a piece of metal (aluminium or mild steel) that would not leave the metal scratched or pitted .

I am thinking more along the lines of a chemical solution rather than a mechanical one.

The article in question is a new aluminium door tread that has been damaged by careless plastering.

I realise that this may not be ME specific but the solution, if there is one, may well be of wider interest as we all pick up bits of "scrap" metal from time to time that has to be cleaned up for machining.

When I worked at a cement works, and got some cement on my car, I was told that the only thing that would remove it was hydroflouric acid. Since it was usefully holding the car together I left it well alone.

Andrew

If you spray WD40 on the cement and let it soak in for a day or two maybe that would work

hydrochloric acid will dissolve cement - used for cleaning bricks.

it will also react with aluminium - so you'd certainly want to test first!

**LINK** suggests weal acids such as citric or sulfamic - i know sulfamic acid is used to remove grout, which is cement based - that may be worth a try.

- russ

HI, while hydroflouric acid has many uses it is pretty nasty stuff to handle. First of all don't put it into a glass container, secoundly don't breath the vapours and thridly it will burn through your skin before you can feel it. See **LINK**

Regards Nick.

Plaster will come off if soaked with water and a good thumb nail. Cement is much the same but is likely to scratch due to sand being.

Bri

Hi Falco,
First is it cement or plaster as this is important for chemical removal methods ? My suggestion is only suitable if you can remove the part. Soak the item in water then put it in the freezer. Repeat this process as required. The water freezing should crack the deposit. Also the different coefficients of expansion should help. (It does not matter if it is cement or plaster for this method.)

Les.

Citric acid dissolves cement / concrete like you wouldn't believe.

Roy.

There is a substance I have not seen before called Belle Clean Concrete dissolver. It reads as if it could work well, but not actually tried it. Tool-net.co.uk list it.

Pete

I'd give brick acid a go. You can buy it in Wickes in a gallon (or whatever the metric is) container. Have used it to get plaster off my aluminium plastering hawk and it worked ok. Don't know what it would do if the ally was lacquered though.

I wouldn't touch hydroflouric acid. I used to work with it when I worked for Sony TVs. They used it to clean the glass which it etches. Corrodes stainless too. Very nasty if it gets on you. We were told it can turn you bones to a jelly by removing the calcium which may sound extreme but I do believe it can attack bone from getting it on the skin.

Hi Falco,

Kettle descaler is also worth a try, not expensive for a test run.

Regards, Bear..

Hi All,

Thanks for the wide range of suggestions. I will work through them, starting with the milder solutions. I will stay clear of Hydroflouric acid I think based on your advice.

My reference to plaster may have been misleading. The sand and cement exterior rendering is commonly and probably incorrectly called plaster here locally and that is what has got to be removed. It is not the interior smooth finish that is much finer and softer.

I still have another door tread to clean and experimenting with the various suggestions should be interesting. Thanks to all

John

If you can get at the back of the aluminium, try warming/heating it behind the cement patches. The different expansion rates should crack off the cement, leaving a slight mark to polish off (which the chemical methods may also do).

Phil

Hi Falco

A high pressure water washer will do it, I have used one to remove cement that has set on bricks, If it is plaster it will only last milliseconds. I did an entire building, it took several days and worked very well, and no acid..........

If you use one on brickwork you may mark damage the bricks if they are soft you will need to reduce the pressure. Metals are not marked all.

You will have to tie your part down on some sort of support first or it may take off if it is light.

I suspect your piece is will be anodised, if so many chemicals will discolour it (including the cement) plain water is unlikely to mark it.

Regards
John

Edited By John McNamara on 22/09/2013 15:12:17

My options are to some extent limited by the fact that the panel in question (basically an aluminium saddle to an outside patio double door) cannot be removed and can only be accessed in full when the door is open.

The use of the power washer is an interesting option but would demand a comprehensive bit of sealing before use as the twin patio doors will have to be open to gain access to the whole. It might be possible though and as John says unlikely to mark the aluminium.

So much for the theory! Next week I'll try to put some of it into practice.

Thanks again all.

John

Hi John,
From Phil's (Robbo) and jason's idea of using differential expansion you could try a steam cleaner.

Les.

Wow, what a lot of replies to a domestic problem with what is supposed to be a 'reliable domestic supplier installation'. I have to say that, any person who crosses your threshold to carry out work on your home can not be trusted to do a good job! That is why i do most of my own domestic challenges. But age now is against me and i wish you all good luck in selecting a reliable domestic installation -- engineer- gas fitter- painter- plumber- decorator- joiner etc!

Based on:

My mother in law (76 years old and energetic) has just had a conservatory fitted. What a fiasco, we were very care full to make sure that all bases were covered and that the builder chosen was in charge and knew what we wanted, he was in charge of the glass and plastic's supplier and was supposed to know what what was required. Ha, the builder got it all wrong and the glass man made a complete bu""er of it!!!!!!!!!!!.

We too now have plaster on the aluminium, however it soaked off with water and it came off the aluminium with no problem, so i am lucky.

Why does no one give a service to be proud of any more!!!!!!!!!!!!!!

Not engineering, but in the general run of the thread created.

Bri

Hi All

A Stark warning about Hydraflouric Acid a 0.5% solution has the potential to Kill you, having worked with this acid for many years with great dread I might add, don't ever endevour to use this unless you are prepared to wear a full set of PPE appropriate to the task before you even start, this isn't a bit of citric that just washes off and usually carries the infamous skull and cross bones label and justifibly so, it made me shudder just to read the suggestion of it's use in a home workshop environment, when we used this as a cleaning solution in power stations etc it was a pre-requesit that the local hospital was informed of it's intended use and in some cases a site attending nurse had to present for immediate response, yes it is a fantastic cleaning acid that loves calcium of which we are an abundant source to it, favour a 10% solution of 40ºC Citric Acid.

Rufus

A short lifetime of pain is only a few drops away with HF