HI Folks - its friday so here 's my challenge for friday pm, I am involved in a building refubishment project as cdmc - we have identified that the contractors will need to replace a powder coating on eaves panels which has blistered and is peeling.

we know the panel has had a chromate dip treatment prior to powder coating but we don't know what type of chromium was used.

Hse quote in eh 40 twa for aluminium metal and oxides as 10 and 4 mg/m3 for inhalable and respirable dust , and a lower twa of 0.5 for chromate compounds 111 and 0.05 for chromate compounds vi it is my understanding that the chromate bonds with the aluminium panel to create aluminium chromate my concern is obviously the dust.

any thoughts on which eh40 standard to use would be great _ i am writing the pci so obviously need to put this info in.
simon

Not sure of the answer but suggest

1) Can you find out who treated it and ask them
2) If there is only a small amout to do treat it as worst case scenario
3) If there is a lot of work to do and number 1 wasn't possible, get it tested for clarification

Sorry not help further

It was very likely a Chromium VI dip - see http://en.wikipedia.org/...omate_conversion_coating

If in any doubt, treat it as the worst case, as already suggested.

It is not likely all Chromium VI, however as you cannot be certain of the ratio it would be best to treat it as stated above, as 100% i.e. worse case.

My advice? Remove it using a chemical agent (low hazard) such as peelaway or similar branded paint remover = problem solved.

Des

Also look to see if there is a water based treatment available so reducing dust [I am not saying that one exists as I am out of touch]

It would be good if cross fertilisation of information and techniques is used between industries as the standard building construction types would learn a lot from engineering and manufacturing [& VV on occasion] i.e. Bring a technology from one industry into another to clean and prep the material

E.g. I have been involved with the cutting of steel [inclusive of stainless] and other materials by water alone [v-high pressure jets] where the water cuts and the residue hold down dust but the builders etc. I have met only know of grinding and similar so create dust where the water cutting systems do not NB: I do not know of any water cutting systems that are used in construction in this country so please do not ask

Additionally if this work is undertaken in an outside area then the risk of inhalation reduces and U you can probably use an asbestos graded hover to draw away much of the dust if it is positioned close enough to the work as the removal process is underway

Its nice to see a CDMC on this site and surly the PC should be asking the question of their people as well?

Powder coating suggests metalwork, suggests shot-blasting to remove along with corroded material?
(detachment of a powder coat suggests some corrosion)
All the things that go with that: specialist contractor, enclosure, potentially nasty primer on remediated surfaces, choice of new finish (where's the Design input?)
Chromate conversion: I'm more conversant with that being applied to aluminium. In that instance, this isn't something that will come off, it's more of a chemical conversion thingy?

Wet work is an option, but you'll have attendant problems in capturing and containing some horrible slurry and keeping EPA/SEPA and Water and Drainage people happy.
Chemical strip might work, but you've then problem of getting the residue off to give you a clean surface for primer.

All in all, perhaps a job for the specialist, and the PC should be in a position to identify and engage the appropriate subbie.

Other option (CDM best option, less work at height and better containment and control of chemical nasties?) is to take the whole lot away to be done at the specialist's site and reinstate them when they're all bright and shiny again.

Hi, my weekend is different! I suggest that you make sure that the substance is not CCA which is Chromated Copper Arsenate, and may need very different approaches - knowing the age of the wood may be a good indicator with regard to treatment. CCA is carcinogenic potentially in different organs, and you may need to consider dust control and also waste management and finally PPE.

If you are using a blasting medium, there are enclosed blasting systems, we use one regulation called Vacublast, minimal dust, can be operator propelled or via remote.

Couldnt find you a direct link but a google search returned a video of them using it to remove lead based paint, could be exactly what your looking for??

Des