Painted Weathering steel in sewage treatment station
Painted Weathering steel in sewage treatment station
(OP)
Hello,
If this forum is not the most adequate to this question, please someone inform me which one is so i can question there.
I was hired to design a steel structure to support a roof and a runway girder. This structure will be located in a sewage treatment station but will not be in constant direct contact with sewage. The runway girder will be used to lift the grill with the wastes one time per day so maybe it will have contact daily with contaminants, although is not immersed.

At first i thought of specify stainless steel but i'm want to know if there are some solution which is adequate and more economical.
CBCA, which is a steel institute in my country(Brazil) has a guide to painting and surface treatment of steel and this guide has a suggestion of a painting stustem for "steel structures which are immersed in effluent and sewage" that is suitable for carbon steel and weathering steel. This system consists of three layers (150µm each) of coal tar epoxy. My first idea is to specify weathering steel with this painting system.
My question is if a system design for steel immersed in sewage is also adequate and economical for steel that has sporadic contact with sewage.
Thanks in advance.
If this forum is not the most adequate to this question, please someone inform me which one is so i can question there.
I was hired to design a steel structure to support a roof and a runway girder. This structure will be located in a sewage treatment station but will not be in constant direct contact with sewage. The runway girder will be used to lift the grill with the wastes one time per day so maybe it will have contact daily with contaminants, although is not immersed.

At first i thought of specify stainless steel but i'm want to know if there are some solution which is adequate and more economical.
CBCA, which is a steel institute in my country(Brazil) has a guide to painting and surface treatment of steel and this guide has a suggestion of a painting stustem for "steel structures which are immersed in effluent and sewage" that is suitable for carbon steel and weathering steel. This system consists of three layers (150µm each) of coal tar epoxy. My first idea is to specify weathering steel with this painting system.
My question is if a system design for steel immersed in sewage is also adequate and economical for steel that has sporadic contact with sewage.
Thanks in advance.
RE: Painted Weathering steel in sewage treatment station
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
RE: Painted Weathering steel in sewage treatment station
Dik, all i now is that it will be near a waste treatment plant. Are you aware of standards or supplier's manuals which define the appropriate painting for the specific substances?
With respect to the Tar modified epoxy, i will avoid it due to the carcinogenicity.
Swazimatt, did you decide to use this specific paints due to some recommendation(Guide, Standard) specific to Waste treatment plants?
I'm using this guide from the brazilian steel institue. The guide has recommendations for industrial environment and also recommendations for elements immersed in effluent and sewage( Which is the coal tar epoxy that dik showed to be carcinogenic).
Maybe the painting for industrial environment is adequate, since sulfur dioxide is common in industrial environments. What do you think?
RE: Painted Weathering steel in sewage treatment station
As far as tar modified epoxies, there may be some that are non-carcinogenic... they are excellent coating materials; check with suppliers.
If critical, you need to determine the effluents chemically and check with major/reputable coating suppliers to determine what is best coating system. It's likely a high build zinc rich epoxy with a top epoxy coating plus a high gloss polyurethane top coat. It's costly... or something of that ilk.
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
RE: Painted Weathering steel in sewage treatment station
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
Your situation is similar to handrails in wastewater treatment plants. These are normally supplied in aluminum or 304SS.
I would recommend the posts be made of aluminum or 304SS. The upper structure can be painted steel. Here are some manufacturers:
3.6 EXTERIOR HIGH-PERFORMANCE COATING SCHEDULE
A. Steel Substrates:
1. First Coat:
a. Sherwin-Williams Company (The); Corothane 1 Gal-Va-Pac Zinc Primer B65G00010 at 3.0-4.0 mils DFT.
b. Tnemec Inc.; Series 90-97 Tnemec-Zinc at 2.5 to 3.5 mils DFT.
2. Second Coat:
a. Benjamin Moore & Co. Corotech V160 Epoxy Mastic Coating @4.6-7.2 DFT
b. Sherwin-Williams Company (The); Dura-Plate 235 Multi-Purpose Epoxy B67W235 at 4.0-8.0 mils DFT
c. Tnemec Inc.; Series N69 Hi-Build Epoxoline II at 3.0 to 5.0 mils DFT.
3. Third Coat:
a. Benjamin Moore & Co. Corotech V500 Acrylic Aliphatic Urethane Coating Gloss or V510 Acrylic Aliphatic Urethane Coating Semi-Gloss at 3.2-4.6 mils DFT
b. Sherwin-Williams Company (The); Acolon 218 HS Polyurethane Gloss B65W611 at 3.0-6.0 DFT.
c. Tnemec Inc.; Series 1074 or 1075 Endura-Shield II at 2.0 to 5.0 mils DFT.
RE: Painted Weathering steel in sewage treatment station
RE: Painted Weathering steel in sewage treatment station
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
Jed, no you're not late. The client is waiting some information about the equipment that will be lifted so started monday the design and i still can make changes. It's a open frame.
Dik, i've asked the client if they can determine the effluent chemically, or if they have already determined, and will check with suppliers to see what they have available for this situation.
Bimr, thank you for your suggestions. I'll check if these suppliers are present in my country (Brazil).
RE: Painted Weathering steel in sewage treatment station
RE: Painted Weathering steel in sewage treatment station
"The decomposition of organic matter produces gases as hydrogen sulfide(H2S), methane(CH4) and carbon dioxide(CO2), among others, which can be present, in large quantities, at the channel entrance."
I really liked the idea proposed by bimr of using stainless steel for the columns and base plates and painted carbon steel for the upper structure, i would have only to carefully detail the connection between them to avoid galvanic corrosion, since the columns will be more exposed to the effluents and the upper structure only to the gases, i think that a painting system adequate to industrial facilites will be enough for the upper structure. Also, the weight incresed for the upper structure considering stainless steel will be greater than for the columns.
RE: Painted Weathering steel in sewage treatment station
theysome are time critical for chemical bonding. In addition the high gloss topcoat is essential because epoxies don't take well to exposure (they dull) and the high gloss provides better topcoat protection than another type of finish surface.Unless exceptional, I would not be using SS for framing. Are they venting these gases to the atmosphere?
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
That`s because the smaller stifness and nonlinearity of the stress-strain diagram on service loads or for other reason?
No, but the roof height over the channel entrance is 6 meters, so i think that there is good natural ventilation.
RE: Painted Weathering steel in sewage treatment station
They tend to be more costly and some sections are not readily available.
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
One more item with stainless; It's hard to weld. The welds need to be cleaned with nasty chemicals (pickling or passivating, I'm never quite sure) or they will get surface rust and you'll get a call from the owner asking you "...why you used stainless, it rusted anyhow?"
RE: Painted Weathering steel in sewage treatment station
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
RE: Painted Weathering steel in sewage treatment station
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
RE: Painted Weathering steel in sewage treatment station
My observations are that high performance coatings last as well as heavy hot dip galvanizing except where mechanical abuse damages the coating.
The coating system above is similar to what I would choose. Your market should have similar offerings from local suppliers of industrial coating systems.