Muntz Metal _2

Ice Melter’s effect on muntz metal

• Calcium Chloride (NYC)(http://www.nyc.gov/html/dsny/downloads/pdf/2011_2012_Snowplan/ManhattanSnow.pdf)

• Although calcium chloride is not flammable, toxic and does not burn, it can produce hydrogen atoms if it reacts with zinc and sodium. It is also corrosive to metals such as brass and steel. Calcium chloride pellets should not be ingested.

• Handbook of Corrosion Data

• By Bruce D. Craig• Table 6• (

http://books.google.com/books?id=KXwgAZJBWb0C&pg=RA1-PT183&lpg=RA1-PT183&dq=Calcium+Chloride+brass&source=bl&ots=RfIYEtyv1k&sig=bt9-L1HlmYne1jJEk4Flk8BA-mg&hl=en&sa=X&ei=46i_T93oLMOQgwfUrN3hCQ&ved=0CFIQ6AEwAg#v=onepage&q=metal%20brass&f=true )

acid rain effect on muntz metal

• The primary emissions responsible for acid deposition are sulfur dioxide (SO2) and oxides of nitrogen (NOx) from the combustion of coal, oil and natural gas. The combustion compounds are transformed into sulfuric and nitric acid and transported downwind before they are deposited– NO x may react with water to make nitric acid:

• 3 Cu + 8 HNO3 → 3 Cu2+ + 2 NO + 4 H2O + 6 NO3-

– The action of hot sulfuric acid on copper turnings produces sulfur dioxide:

• Cu + 2 H2SO4 → CuSO4 + SO2 + 2 H2O

Dezincification• Dezincification selectively removes zinc from the alloy,

leaving behind a porous, copper-rich structure that has little mechanical strength.

• An in-service valve suffering from dezincification has a white powdery substance or mineral stains on its exterior surface.

• Copper-zinc alloys inhibited with small amounts of arsenic, antimony, or phosphorus are resistant to this form of corrosion.

Copper Alloy’s SCC (Stress corrosion cracking )

Copper Alloys (excluding Cu-Ni)

N2O4 high Low (Temp) Trans granular: cracks go across the grains.

Ammoniacal solutions and other nitrogenous

Low (Temp) Low

By choosing a material that is not susceptible to SCC in the service environment and by processing and fabricating it correctly, subsequent SCC problems can be avoided.

General corrosion

• General corrosion is defined as well distributed metal loss of an nitro surface with little or no localized penetration.

• Copper corrodes at negligible rates in unpolluted air, water, and nonoxidizing acids. Copper alloys resist many saline solutions, alkaline solutions, and organic chemicals. Copper and its alloys are susceptible to rapid attack in oxidizing acids, oxidizing heavy-metal salts, and sulfur and ammonia and their compounds. Air or dissolved oxygen in nonoxidizing acids accelerates otherwise low corrosion rates.

Wax coating (Hot Wax)• For most collectible brass and bronze artifacts, the best coating we can

generally recommend is wax. Wax provides a relatively flexible coating that is easily applied and that can be renewed. It can be used on top of original patinas and lacquers that you do not wish to disturb, as long as they are cleaned first.

• Process: Wax has been used as a protective barrier coating on outdoor metal monuments for thousands of years and the techniques for its application have remained virtually unchanged over time. Hot waxing usually refers to a procedure whereby the applicator brush-applies a paste mixture of wax and solvents to a heated metal surface.

• Problems: it is extremely tedious and time-consuming and, on certain surfaces, the application of the wax can be either too heavy or too light. Additionally, because a brush or rag is used in the application procedure, the final integrity of the finish can be compromised by brush hairs, lint residue from the rags, and streaks caused by the brush hairs.

the main wax properties and corresponding effects imparted or improved in paint, coating and ink formulations.

Type Properties Main Performances

Carnauba

· High melting naturally occuring wax · Different grades (T1, T2, T3) · Hard & brittles · Excellent clarity · Generally Recognised As Save

· Slip & Lubricity · Anti-Blocking · Mar Resistance

Paraffin

· Various grades, hence properties depending on refinement degree · Hard to oily feeling · Mainly composed of straight alkane chains, hence some parafffin's have good crystalline structure, giving excellent barrier effects against water repellency · Very low polarity

· Anti-Blocking · Water Repellency · Slip & Lubricity

PE

· Obtained by polymerization of Ethylene monomers · Various grades, hence properties depending on Mw and polymerisation process · Two main families: LDPE and HDPE (Low and High Density PE) whose difference is the extend and type of branching · LDPE's display more thoughness, better scuff / mar resistance and are more flexible · HDPE's contribute to better slip properties and abrasion resistance

· Slip · Abrasion Resistance · Anti-Blocking

PP · Obtained by polymerization of propylene monomers · Good film toughness but poor slip & lubricity properties · Not really a wax but often classify as such because of impact to surface properties

· Anti-Slip · Anti-Blocking · Abrasion Resistance

PTFE

· Obtained by polymerization of C2F4 monomers · High melting point and outstanding heat resistance properties (up to 600°F) · Give the lowest known CoF, hence excellent slip & lubricity, anti-blocking and abrasion resistance · Chemically inert · Not really a wax but often classify as such because of impact to surface properties

· Slip & Lubricity · Anti-Blocking · Abrasion Resistance

PP = polypropylene PE = polyethyleneHDPE = High Density Polyethylene PTFE = Polytetrafluoroethylene

Powder Coating

• Powder coating is a method used to apply a decorative or protective coating to variety of materials in both industrial and commercial applications. The powder coating process involves the dry application of finely ground particles of pigment and resin to surfaces prior to a curing process. Unlike liquid coatings, each individual powder particle contains the entire coating formulation (pigment, resin, fillers, and modifiers); there are no solvents in powder coating. The applied powder material is then heated to a temperature sufficient to melt and cure the resin. After cooling, the coating is complete; there is no cure time beyond the cool-down period.

Lacquering

• On large areas of metal, a spray-applied lacquer achieves the most even and durable finish.

• Poorly applied lacquers can actually cause more severe corrosion if small areas are left exposed.

• The process is a cold-process, there is no heat involv3ed and the underlying substrate will not be impacted: no warping, shrinking or distortion of any kind.

• Once painted, the metal is very durable, will not delaminate, crack, chip or peel, and has all the surface characteristics of a solid metal object. (Doubtable)

• Completely change the finish of an existing piece by applying or incorporating metal, creating a new look with longevity.