Coated metal strip

A corrosion-resistant architectural material which is essentially lead free and is not highly reflective. The coating on the material is a two-phase metallic coating comprised of zinc and tin. The tin-zinc coating may also include aluminum, antimony, bismuth, copper, magnesium, nickel and/or titanium to improve the coating process and/or improve the properties of the tin-zinc coating.

The present invention relates to the art of metal architectural materials 
and more particularly to an architectural strip material that is 
environmentally friendly while providing long life and desired 
colorization. 
INCORPORATION BY REFERENCE 
As background material, so that the specification need not specify in 
detail what is known in the art, Assignees' U.S. Pat. Nos. 4,987,716 and 
4,934,120 illustrate metal roofing systems of the type to which this 
invention can be used and are incorporated herein by reference. U.S. 
patent application Ser. No. 000,101 filed Jan. 4, 1993, now abandoned 
illustrating a process of hot-dip coating roofing materials, is also 
incorporated herein by reference. In addition, various coatings for strip 
material disclosed in Assignee's U.S. patent application Nos. 042,649 
filed Apr. 5, 1993 and 175,523 filed Dec. 30, 1993 are incorporated 
herein. U.S. Pat. No. 3,231,127 is incorporated herein for purposes of 
establishing the eutectic point of a tin-zinc alloy. 
The present invention relates to the art of coating a metal material and 
more particularly to the coating of a strip of metal material with a 
hot-dipped coating of zinc and tin; however, the invention has much 
broader applications. 
BACKGROUND OF THE INVENTION 
Over the years, architectural materials, such as metal roofing systems and 
metal siding systems, made of pliable metals in various sheet gauge 
thicknesses have been used. Metals such as carbon steel, stainless steel, 
copper and aluminum are the most popular types of metal. These 
architectural metal materials are commonly treated with 
corrosion-resistant coatings to prevent rapid oxidation of the metal 
surface, thereby extending the life of the materials. A popular 
corrosion-resistant coating for carbon steel and stainless steel is a 
terne coating. Terne coating has been the predominate and the most popular 
coating for roofing materials due to its relatively low cost, ease of 
application, excellent corrosion-resistant properties and desirable 
colorization during weathering. The terne coating is an alloy typically 
containing about 80% lead and the remainder tin. The coating is generally 
applied to the architectural materials by a hot-dip process wherein the 
material is immersed into a molten bath of terne metal. Although terne 
coated sheet metals have exhibited excellent resistant properties and have 
been used in a variety of applications, the terne coating has been 
questioned in relation to its impact on the environment. Environmental and 
public safety laws have been recently proposed and/or passed prohibiting 
the use of materials containing lead. Because the terne alloy contains a 
very high percentage of lead, materials coated with terne have been 
prohibited in various types of usages or applications such as aquifer 
roofing systems. The concern of lead possibly leaching from the terne 
coating has made such coated materials inadequate and/or undesirable for 
several types of building applications. The terne alloy has a further 
disadvantage in that the newly applied terne is very shiny and highly 
reflective. As a result, the highly-reflective coating cannot be used on 
buildings or roofing systems such as at airports and military 
establishments. The terne coating eventually loses its highly-reflective 
properties as the components within the terne coating are reduced 
(weathered); however, the desired amount of reduction takes approximately 
1 1/2 to 2 years when the terne coating is exposed to the atmosphere, thus 
requiring the terne metals to be stored over long periods of time prior to 
being used in these special areas. The storage time is significantly 
prolonged if the terne-coated materials are stored in rolls and the rolls 
are protected from the atmosphere. 
Tin coating of carbon steel is a well-known process for use in the food 
industry. However, in the specialized art of architectural materials, a 
tin coating for architectural materials has not been used until just 
recently as disclosed in U.S. Pat. No. 5,314,758. The most popular process 
for applying a tin coating to carbon steel for use in the food industry is 
by an electrolysis process. In an electrolysis process, the coating 
thickness is very thin and typically ranges between 3.8.times.10.sup.-4 to 
20.7.times.10.sup.-4 mm (1.5.times.10.sup.-5 to 8.15.times.10.sup.-5 in.). 
Furthermore, the equipment and materials needed to properly electroplate 
the metal materials are very expensive and relatively complex to use. The 
expense of applying an electroplated-tin coating and the limited 
obtainable thicknesses of the tin coating are a disadvantage for using 
such a process for building and roofing materials. 
A hot-dip process for applying the tin coating may be used; however, if the 
architectural materials are not properly prepared and the coating is not 
properly applied to the roofing materials, minute areas of discontinuity 
in the tin coating may occur resulting in non-uniform corrosion 
protection. This is especially a problem when the tin is applied to 
stainless steel materials by a hot-dip process. Tin is not 
electroprotective to steel under oxidizing conditions. Consequently, 
discontinuities in the tin coating result in the corrosion of the exposed 
metal. Tin coatings have the further disadvantage of having a 
highly-reflective surface. As a result, architectural materials coated 
with a tin coating cannot be used in an environment where 
highly-reflective materials are undesirable until the coated materials are 
further treated (i.e. painted) or the tin is allowed time to oxidize. 
Coating architectural materials with zinc metal, commonly known as 
galvanization, is another popular metal treatment to inhibit corrosion. 
Zinc is a highly desirable metal to coat architectural materials with 
because of its relatively low cost, ease of application (i.e. hot-dip 
application) and excellent corrosion resistance. Zinc is also 
electroprotective to steel under oxidizing conditions and prevents the 
exposed metal, due to discontinuities in the zinc coating, from corroding. 
This electrolytic protection extends away from the zinc coating over 
exposed metal surfaces for a sufficient distance to protect the exposed 
metal at cut edges, scratches, and other coating discontinuities. With all 
of the advantages of using zinc, zinc coatings have several disadvantages 
that make it undesirable for many types of building applications. Although 
zinc coatings will bond to many types of metals, the formed bond is not 
strong and can result in the zinc coating flaking off the building 
materials. Zinc does not bond well on standard stainless steel materials. 
Zinc does not form a uniform and/or thick coating in a hot-dip process for 
stainless steel. As a result, discontinuities of the coating are usually 
found on the stainless steel surface. Zinc is also a very rigid and 
brittle metal and tends to crack and/or flake off when the building 
materials are formed on site, i.e. press fitting of roofing materials. 
When zinc begins to oxidize, the zinc coating forms a white powdery 
texture (zinc oxide). The popular grey, earth tone color is never obtained 
from pure zinc coatings. 
Electroplating a tin and zinc mixture onto a steel sheet is disclosed in 
Japanese Patent Application No. 56-144738 filed Sep. 16, 1981. The 
Japanese patent application discloses the plating of a steel sheet with a 
tin and zinc mixture to form a coating of less than 20 microns thick. The 
Japanese patent application discloses that after plating pin hole exist in 
the coating and subject the coating to corrosion. The pin holes are a 
result of the crystalline layer of a tin and zinc mixture which slowly 
forms during the plating process. The charged tin and zinc atoms in 
combination with the atomic structure of the atoms and formed crystal 
structure of a tin and zinc mixture prevents a uniform coating from being 
formed on the plated steel sheet. Consequently, the crystalline 
depositions must be covered with a chromate or phosphoric acid to fill the 
pin holes and prevent immediate corrosion. The Japanese patent application 
also discloses that a preplated layer of nickel, tin or cobalt on the 
steel sheet surface is needed so that the plated tin and zinc mixture will 
adhere to the steel sheet. Such electroplating techniques as disclosed in 
the Japanese patent application cost a tremendous amount of time and money 
and are not a commercially successful product. 
The coating of steel articles with a tin, zinc and aluminum mixture is 
disclosed in U.S. Pat. No. 3,962,501 issued Jun. 8, 1976. The '501 patent 
discloses that the tin, zinc and aluminum mixture resists oxidation and 
maintains a metallic luster. The '501 patent discloses that the coating is 
applied by immersing a steel article into the molten alloy bath and 
subsequently withdrawing the steel article. The '501 patent also discloses 
that a molten tin-zinc alloy bath containing 3-97% zinc is very 
susceptible to oxidation at the surface thus producing viscous oxides 
which causes severe problems with the process of immersing the steel 
articles into the molten alloy and subsequently removing the steel article 
from the molten alloy. Further, while the steel article is in the molten 
alloy, a large amount of dross is produced which results in non-uniformity 
of the coating and formation of pin holes. The '501 patent discloses that 
the addition of up to 25% aluminum to the tin and zinc mixture inhibits 
dross formation during immersion of the steel article, prevents Zn-Fe 
alloy formation and reduces the viscous oxide formation on the molten bath 
surface. The '501 patent does not teach the use of a continuous, hot dip 
coating process which resolves the viscous oxide problem and dross 
formation problem. The '501 patent also discloses the formation of a 
highly reflective coating which cannot be used in many building 
applications. 
Due to the various environmental concerns and problems associated with 
corrosion-resistant coatings applied to metal architectural materials, 
there has been a demand for a coating which can be easily and successfully 
applied to materials that protect the materials from corrosion, does not 
have a highly-reflective surface subsequent to application, can be applied 
by a continuous hot-dip process, weathers to a grey, earth tone color and 
allows the materials to be formed at the building site. 
SUMMARY OF THE INVENTION 
The present invention relates to a corrosion-resistant, environmentally 
friendly coating formulation for use on architectural materials wherein 
the coating is environmentally friendly, has a low lead content and 
weathers to form a non-highly-reflective desirable surface which resembles 
the grey, earth tone color of weathered terne. 
In accordance with the principal feature of the invention, there is 
provided an architectural material typically of stainless steel, carbon 
steel or copper coated with a tin-zinc alloy. Other materials can also be 
coated by the tin-zinc coating such as nickel alloys, aluminum, titanium, 
bronze, etc. The tin-zinc coating is a two phase metal coating primarily 
comprising zinc and tin. The tin-zinc combination provides for a 
corrosion-resistant coating that protects the surface of the architectural 
material from oxidation, which is environmentally friendly thus immune 
from the prejudices associated with lead containing materials, which forms 
a gray surface upon weathering which is very similar to weathered terne, 
and which is not highly reflective. 
In accordance with another aspect of the present invention, the tin and 
zinc content of the tin-zinc alloy makes up at least 75 weight percent of 
the alloy and preferably makes up to at least 80 weight percent of the 
alloy and more preferably at least 90 weight percent of the alloy. The 
zinc content of the alloy is preferably at least 7 weight percent and over 
9 weight percent for a two-phase alloy as established in U.S. Pat. No. 
3,231,179 and preferably does not exceed about 85 weight percent of the 
alloy. 
In accordance with another aspect of the present invention, the coated 
metal material is pretreated prior to applying the tin-zinc coating. If 
the metal material is stainless steel, the pretreatment process is 
preferably similar to the process disclosed in Assignees' U.S. patent 
application Ser. No. 000,101 filed on Jan. 4, 1993 and incorporated 
herein. "Stainless steel" in the application means a large variety of 
alloy metals containing chromium and iron. The alloy may also contain 
other elements such as nickel, carbon, molybdenum, silicon, manganese, 
titanium, boron, copper, aluminum, nitrogen and various other metals or 
compounds. Elements such as nickel can be flashed (electroplated) onto the 
surface of the chromium-iron alloy or directly incorporated into the 
chromium-iron alloy. The pretreatment process includes aggressive pickling 
and chemical activation of the metal material surface. 
Prior to aggressive pickling and chemical activation of the metal material, 
the metal material may be treated with an abrasive and/or absorbent 
material and/or subjected to a solvent or other type of cleaning solution 
to remove foreign materials and oxides from the metal material surface. 
The aggressive pickling process is designed to remove a very thin surface 
layer from the metal material surface. The removal of a very thin layer 
from the surface of the metal material results in the removal of oxides 
and other foreign matter from the metal material surface thereby 
activating the surface prior to applying the tin-zinc coating. When 
coating stainless steel, it is especially important to activate the 
stainless steel surface in order to form a strong bonding and uniformly 
coated tin-zinc coating. The activation of a stainless steel material, as 
with other metal materials, is accomplished by removing the oxides on the 
surface of the metal material. The removal of a chromium oxide film from 
the stainless steel surface activates the stainless steel material 
surface. Testing of stainless steel materials has revealed that the 
chromium oxide film interferes with the bonding of the tin-zinc coating 
and does not allow for thick and/or uniform tin-zinc coatings to be 
formed. Oxides on other metal materials also adversely effect the bonding 
and coating thickness of the tin-zinc coating. The aggressive pickling 
process removes the detrimental oxide layer to facilitate in the formation 
of a strong bonding and uniform tin-zinc coating. 
The aggressive pickling process also may slightly etch the metal material 
surface to remove a very thin layer of the surface. The rate of etching is 
not the same throughout the surface of the metal material thereby forming 
microscopic valleys on the metal material surface which increases the 
surface area for which the tin-zinc coating can bond to the metal 
material. 
The aggressive pickling process includes the use of a pickling solution 
which removes and/or loosens the oxide from the metal material surface. 
The pickling solution contains various acids or combinations of acids such 
as hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, 
phosphoric acid and/or isobromic acid. A specially formulated pickling 
solution should be used if the metal material is stainless steel since the 
activation of a stainless steel surface is not properly accomplished by 
use of prior art pickling solutions containing only sulfuric acid, nitric 
acid or hydrochloric acid. The specially formulated pickling solution 
contains a special combination of hydrochloric acid and nitric acid. This 
special dual acid formulation was found to be surprisingly effective in 
the rapid removal of chromium oxide from stainless steel substrates. The 
dual acid composition of the pickling solution contains 5-25% hydrochloric 
acid and 1-15% nitric acid and preferably about 10% hydrochloric acid and 
3% nitric acid. The temperature of the pickling solution should be 
controlled to maintain the proper activity of the pickling solution. The 
temperature of the pickling solution is generally above 80.degree. F. and 
usually between 120.degree.-140.degree. F. and preferably 
128.degree.-133.degree. F. 
The pickling solution may be agitated to prevent the solution from 
stagnating, varying in concentration and/or to remove gas pockets which 
form on the metal material surface. The metal material may also be 
scrubbed during the aggressive pickling process to facilitate in the 
activation of the metal material surface. 
Generally, only one pickling vat is needed to properly activate the metal 
material surface; however, additional pickling vats may be used. The 
pickling vats are generally twenty-five feet in length; however, the size 
of the vat may be longer or shorter. The total time for aggressively 
pickling the metal material is usually less than 10 minutes, typically 
less than a minute and preferably about 10 to 20 seconds to properly 
activate the metal material. If the metal material is a sheet strip and is 
to be processed in a continuous process, the pickling vats are usually 25 
feet in length and the sheet strip is run through the pickling vats at a 
rate usually between 1-150 ft/min and typically between 50 to 115 ft/min 
thereby subjecting the metal material to the pickling solution in each 
pickling vat for preferably less than one minute. The sheet strip 
thickness is usually less than 0.1 inch and preferably less than 0.03 inch 
so that the sheet strip can be properly guided through the continuous 
process, i.e. unroll the strip material and roll up the coated strip 
material. 
Once the metal material has been aggressively pickled, the metal material 
may further be treated in a chemical activation process. The chemical 
activation process further removes oxides and foreign material from the 
metal material by subjecting the metal material surface to a deoxidizing 
agent. Due to the difficulty in removing oxides from stainless steel 
materials, a stainless steel material should be treated in the chemical 
activation process after the stainless steel material has been treated in 
the aggressive pickling process. Various types of deoxidizing solutions 
can be used. For the treatment of a stainless steel material, zinc 
chloride has been found to be an excellent deoxidizing solution. 
The zinc chloride acts as both a deoxidizer and a protective coating for 
the metal material surface. The temperature of the zinc chloride solution 
is generally kept at ambient temperature (60.degree.-90.degree. F.) and 
may be agitated to maintain a uniform solution concentration. Small 
amounts of hydrochloric acid may also be added to the deoxidizing solution 
to further enhance oxide removal. Preferably, hydrochloric acid is added 
to the zinc chloride when treating a stainless steel material. The time 
the metal material is subjected to the deoxidizing solution is usually 
less than 10 minutes. If the metal material is in sheet strip form and is 
being processed in a continuous process, the deoxidization solution tanks 
are preferably 25 feet in length and the metal material is subjected to 
the deoxidation solution for preferably less than one minute. 
The pretreatment process may also include the maintaining of a low oxygen 
environment prior to and/or subsequent to subjecting the metal material to 
the aggressive pickling process and/or chemical activation process. The 
maintenance of a low oxygen environment inhibits the formation and/or 
reformation of oxides on the metal material surface. The low oxygen 
environment may take on several forms. Two examples of low oxygen 
environments are the formation of a low oxygen-containing gas environment 
about the metal material or the immersion of the metal material in a low 
oxygen-containing liquid environment. Both these environments act as 
shields against atmospheric oxygen and prevent and/or inhibit oxides from 
forming. If the metal material is stainless steel, the low oxygen 
environment should be maintained throughout the pretreatment process of 
the stainless steel material to just prior to the coating of the stainless 
steel material with the tin-zinc coating. The non-oxidized surface of a 
stainless steel material is highly susceptible to rapid reoxidation when 
in contact with oxygen. By creating a low oxygen environment about the 
stainless steel material, new oxide formation is inhibited and/or 
prevented. 
Examples of low oxygen gas environments include nitrogen, hydrocarbons, 
hydrogen,noble gasses and/or other non-oxidizing gasses. Generally, 
nitrogen gas is used to form the low oxygen gas environment. Examples of 
low oxygen liquid environment include non-oxidizing liquids and/or liquids 
containing a low dissolved oxygen content. An example of the latter is 
heated water sprayed on the surfaces of the metal material; however, the 
metal material may also be immersed in the heated water. Heated water 
contains very low levels of dissolved oxygen and acts as a shield against 
oxygen from forming oxides with the metal material. The spray action of 
the heated water may also be used to remove any remaining pickling 
solution or deoxidizing solution from the metal material. Generally, the 
temperature of the heated water is maintained above 100.degree. F. and 
typically about 110.degree. F. or greater so as to exclude the unwanted 
dissolved oxygen. 
In accordance with yet another aspect of the present invention, the 
tin-zinc coating is applied to the metal material by a hot-dip process. 
The hot-dip process is designed to be used in a batch or a continuous 
process. Preferably, the coating of the metal materials is by a continuous 
hot dip process similar to the one disclosed in Assignee's U.S. patent 
application Ser. No. 000,101. The metal material is coated in the hot-dip 
process by passing the metal material through a coating vat which contains 
the molten tin-zinc alloy. The coating vat may include a flux box whereby 
the metal material passes through the flux box and into the molten 
tin-zinc alloy. The flux box typically contains a flux which has a lower 
specific gravity than the molten tin-zinc, thus the flux floats on the 
surface of the molten tin-zinc the flux within the flux box acts as the 
final surface treatment of the metal material. The flux removes residual 
oxides from the metal material surface, shields the metal material surface 
from oxygen until the metal material is coated with the tin-zinc alloy, 
inhibits the formation of viscous oxides at the point where the metal 
material enters the molten tin-zinc alloy and inhibits dross formation on 
the metal material. The flux preferably contains zinc chloride and may 
contain ammonium chloride. The flux solution typically contains 
approximately 30-60 weight percent zinc chloride and up to about 40 weight 
percent ammonium chloride and preferably 50% zinc chloride and 8% ammonium 
chloride; however, the concentrations of the two flux agents may be varied 
accordingly. 
Once the metal material passes through the flux, the metal material enters 
the molten tin-zinc alloy. The temperature of the molten tin-zinc is at 
least 449.degree. F. The tin-zinc alloy must be maintained above its 
melting point or improper coating will occur. Tin melts at 232.degree. C. 
(450.degree. F.) and zinc melts at 420.degree. C. (788.degree. F.). The 
larger the content of zinc, the closer the melting point of the tin-zinc 
coating approaches 420.degree. C. Metals such as iron, nickel, aluminum, 
titanium, copper, magnesium, bismuth and antimony which may be added to 
the tin-zinc alloy can also raise the melting point of the alloy. For 
instance, the alloy is heated to temperatures as high as 538.degree. C. 
(1000.degree. F.) when copper is added to the tin-zinc alloy. In order to 
accommodate for the temperatures, the coating vat is made to withstand 
these higher temperatures. A protective material such as palm oil is 
preferably placed over the surface of the molten alloy. The protective 
material has a specific gravity which is less than the molten alloy so 
that the protective materials float on the surface of the molten alloy. 
The protective material shields the molten alloy from the atmosphere 
thereby preventing oxides from forming on the molten alloy surface. The 
protective material also inhibits dross formation on the coated material 
as the coated material exits from the coating vat. If the protective 
material is palm oil, the melting point of the alloy must be below the 
650.degree. F. degrading point for the palm oil. For coating alloys having 
higher melting point temperatures, special oils, fluxes, or other 
materials and/or special cooling procedures for the palm oil will be 
employed. 
The time period for applying a tin-zinc coating to the metal material is 
usually less than 10 minutes. If the metal material is in sheet strip form 
and is being processed in a continuous process, the time period for 
applying the tin-zinc coating is typically less than two minutes and 
usually from 10 to 30 seconds. 
After the metal material has been coated, the coated metal material is 
usually cooled. The cooling of the coated metal material can be 
accomplished by spraying the coated metal material with a cooling fluid 
such as ambient temperature water and/or immersing the coated metal 
material in a cooling liquid such as ambient temperature water. The 
cooling of the coated metal material usually is less than one hour and 
preferably is less than a few minutes. 
The thickness of the tin-zinc coating is preferably regulated by coating 
rollers. The thickness of the tin-zinc coating is typically 0.0003-0.05 
inch. Spray jets which spray the molten tin-zinc alloy onto the metal 
material may be used to ensure a uniform and continuous coating on the 
metal material. The continuous hot-dip process disclosed in Ser. No. 
000,101 can be used to coat architectural materials made of metals such as 
stainless steel, carbon steel, aluminum, copper, titanium and bronze. 
In accordance with another aspect of the invention, bismuth, antimony, 
nickel, aluminum, titanium, copper and/or magnesium may be added to the 
tin-zinc coating to enhance the physical properties of the tin-zinc alloy, 
improve corrosion resistance, improve grain refinement, inhibit oxidation 
of the molten alloy, inhibit dross formation during coating, and/or 
inhibit the crystallization of the tin. When tin crystallizes, the bonding 
of the tin-zinc coating to the metal materials may weaken resulting in 
flaking of the coating. The addition of small amounts of bismuth and/or 
antimony in an amount of at least 0.05 weight percent prevents and/or 
inhibits the crystallization of the tin. Bismuth and/or antimony also 
enhances the hardness, strength mechanical properties and corrosion 
resistance of the tin-zinc coating. Nickel has been found to provide 
additional corrosion protection to the tin-zinc alloy especially in 
alcohol containing environments. Copper is added, in addition to its 
stabilizing properties, as a coloring agent to reduce the reflective 
properties of the newly applied alloy and/or to obtain the desired 
coloring of the weathered coating. Copper also improves the corrosion 
resistance of the tin-zinc alloy especially in marine environments. 
Magnesium has been found to improve the flow or coating properties of the 
tin-zinc alloy so that more uniform coating is applied to the metal 
material. Magnesium also reduces the anodic characteristics of the coating 
to further increase the corrosion resistance of the coating. The magnesium 
may also reduce oxidation of the molten alloy and/or reduce dross 
formation during coating. Aluminum is added to the alloy to inhibit 
oxidation of the molten alloy and to reduce dross formation on the 
coating. Aluminum also reduces the thickness of the intermetallic Fe-Zn 
layer so as to improve the formability of the coated metal material. 
Titanium is added to the alloy to improve the grain refinement of the 
coated alloy and hardness and strength of the alloy. Titanium also 
prevents oxidation of the molten alloy and helps reduce dross formation. 
In accordance with another feature of the present invention, the tin-zinc 
coating is essentially lead free. The lead content is maintained at 
extremely low levels not exceeding 0.05 weight percent. Preferably, the 
lead content is maintained at much lower weight percentage levels so as to 
dispense with any environmental concerns associated with the tin-zinc 
coating. 
In accordance with yet another feature of the present invention, the 
tin-zinc coating composition is such that the coated materials can be 
formed on site without the tin-zinc coating cracking and/or flaking off. 
The amount of zinc in the tin-zinc coating is controlled such that the 
coating does not become too rigid and brittle. 
In accordance with still another aspect of the present invention, the metal 
material is plated with a nickel barrier prior to applying the tin-zinc 
coating to provide additional corrosion resistance, especially against 
halogens such as chlorine. The nickel barrier is applied to the metal 
materials to form a thin layer. Although the tin-zinc coating provides 
excellent protection against most of these corrosion-producing elements 
and compounds, compounds such as chlorine have the ability to sometimes 
penetrate the tin-zinc coating and attack and oxidize the surface of the 
metal materials thereby weakening the bond between the metal material and 
the tin-zinc coating. The nickel barrier has been found to provide an 
almost impenetrable barrier to these elements and/or compounds which in 
fact penetrate the tin-zinc coating. Due to the very small amount of these 
compounds penetrating the tin-zinc coating, the thickness of the nickel 
barrier can be maintained at thin thicknesses while still maintaining the 
ability to prevent these components from attacking the metal material. The 
tin-zinc coating and thin nickel coating effectively complement one 
another to provide superior corrosion resistance. 
In accordance with an aspect of this invention, the metal strip is provided 
in a large coil, passed through a preplating bath generally without 
preheating and then moved continuously as a continuous moving strip 
through the bath containing a coating alloy of zinc and tin with tin being 
at least a sufficient amount to overcome the galvanizing of the strip. The 
zinc tin alloy is not merely zinc with a small amount of tin to trim the 
galvanizing of the moving strip. It is common practice to continuously 
galvanize moving strip. This invention is different in that the bath 
contains a major amount of tin to change the galvanizing properties and 
appearance of the strip. The coated strip is then recoiled for shipment 
and use in mass production of products, such as gasoline tanks for motor 
vehicles. Without changing the coating ease of the two phase alloy 
including zinc and a major amount of tin, i.e. at least about 20% tin, the 
alloy may include copper of about 1%, but preferably not more than about 
2.7% by weight of coating material. 
Thus, a preferred embodiment is a zinc-tin coating alloy with copper up to 
2.7%. This coating material increases corrosion-resistance, especially in 
marine environments. The copper is added as brass. 
Another improvement to the zinc-tin alloy with copper is the further 
inclusion of small controlled amounts of aluminum. Typically, the aluminum 
content is up to 0.5% and preferably about 0.3%. This preferred embodiment 
is a two-phase zinc-tin coating alloy with copper and up to 0.5% aluminum. 
The aluminum is added as an alloy of aluminum, copper and magnesium. 
It has been found that titanium prevents oxidation and improves the grain 
refinement of the zinc-tin coating alloy. Preferably, up to 0.15% titanium 
can be used. This preferred embodiment includes the novel two-phase 
zinc-tin alloy with titanium up to about 0.15%. 
Antimony improves corrosion-resistance of the two-phase zinc-tin coating 
alloy. In a preferred embodiment, the coating material is the zinc-tin 
alloy with antimony up to 5.5%, and preferably about 1.0%. 
As an example of a coating material of the invention, the material has a 
base of the zinc-tin alloy with: 
______________________________________ 
Copper up to: 2.7% 
Aluminum up to: 0.5% 
Titanium up to: 0.15% 
Antimony up to: 5.5% 
______________________________________ 
As another example, the zinc-tin alloy has: 
______________________________________ 
About 1.0% copper 
About 0.3% aluminum 
About 1.0% antimony 
______________________________________ 
The alloy and additions above have further examples adding bismuth up to 
1.7%; magnesium up to 0.4% and nickel up to 1.0%. Further, the basic 
coating alloy with additives can be coated on a moving strip with a flash 
of nickel to improve corrosion. 
The strip is preferably steel strip of less than about 0.10 inches 
(preferably less than about 0.03 inches) and the coating is greater than 
about 0.0003 inches and preferably 0.001-0.002 inches. The strip must be 
continuously moving to give uniformity of coating, ability to airknife and 
to provide any commercial success of the product. The invention is a 
two-phase alloy, not zinc with a minor additive of tin, copper, titanium, 
aluminum, antimony, etc. The tin modifies the zinc, as used in 
galvanizing, to achieve a non-galvanized continuous coating. 
The primary object of the present invention is the provision of an 
architectural material coated with a metallic coating which is highly 
corrosive resistant. 
Another object of the present invention is the provision of an 
architectural material treated with a metallic coating that is not highly 
reflective. 
Yet another object of the present invention is a metallic coating, as 
defined above, which is a two phase system comprised of tin and zinc. 
Still another object of the present invention is the provision of an 
architectural material having a tin-zinc coating which weathers to a grey, 
earth tone color. 
Yet another object of the present invention is the provision of a roofing 
material having a tin-zinc metallic coating which is essentially lead 
free. 
Still yet another object of the present invention is to provide a two 
phase, tin-zinc metallic coating applied to a base metal sheet which 
coated sheet can be formed and sheared to form various building and 
roofing components that can be subsequently assembled on site without the 
metallic coating flaking off, chipping, and/or cracking. 
Still another object of the present invention is the provision of providing 
a tin-zinc coated material which can be preformed into roof pans and 
subsequently seamed on site either by pressed seams or soldered seams into 
waterproof joints. 
Another object of the present invention is the provision of applying a thin 
nickel barrier to the surface of the metal material prior to applying the 
tin-zinc coating. 
Yet another object of the present invention is the provision of coating an 
architectural material by a continuous, hot-dipped process. 
Still yet another object of the present invention is the addition of nickel 
to the tin-zinc alloy to increase the corrosion resistance and other 
physical properties of the alloy. 
Another object of the present invention is the addition of a coloring agent 
to the tin-zinc alloy to dull the color of the alloy. 
Yet another object of the present invention is the addition of magnesium to 
the tin-zinc alloy to improve the flow characteristics and corrosion 
resistance of the alloy. 
Another object of the present invention is the addition of titanium to the 
tin-zinc alloy to positively affect grain refinement in the coated alloy. 
Yet another object of the present invention is the addition of titanium to 
the .tin-zinc alloy to reduce oxidation of the molten tin-zinc alloy. 
Still yet another object of the present invention is the addition of 
aluminum to the tin-zinc alloy to reduce oxidation of the molten tin-zinc 
alloy. 
These and other objects and advantages will become apparent to those 
skilled in the art upon reading of the detailed description of the 
invention set forth below.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The tin-zinc coating is a two phase metallic coating which, when applied to 
stainless steel, low carbon steel or copper material, forms a highly 
corrosion-resistant coating that reduces the corrosion of the metal 
materials when exposed to the atmosphere. The tin-zinc coating contains a 
large weight percentage of zinc and tin. It has been discovered that by 
adding zinc in the amounts of at least 7 weight percent of the tin-zinc 
alloy and over 9 weight percent for a two-phase alloy, the corrosion 
resistance of the two phase metallic coating is significantly increased as 
compared to a protective coating essentially composed of tin. Historically, 
it was believed that two phase systems provided less corrosion resistance 
protection than single phase systems. This belief was partially derived 
from the fact that the bonding between different types of metals is 
irregular and sometimes weaker, thus making the coating more susceptible 
to corrosion. Although the exact reasons for this physical phenomenon of 
increased corrosion resistance due to the combination of zinc and tin is 
unknown to the inventors, it has been found that by adding zinc to tin, 
the two phase metallic coating exhibits corrosive-resistant properties 
which exceed that of tin coatings, zinc coatings and, in some 
environments, that of a terne coating. 
The tin content of the alloy is preferably at least 15 weight percent of 
the alloy. The zinc content of the alloy is preferably at least 20 weight 
percent of the alloy. The tin plus zinc content of the tin-zinc alloy is 
typically at least about 80 weight percent and preferably at least about 
90 weight percent and can make up about 100 weight percent. 
The tin-zinc coating is electroprotective under oxidizing conditions which 
inhibits oxidation of exposed metal near the tin-zinc coating. As a 
result, minor discontinuities in the tin-zinc coating do not result in 
oxidation of the exposed metal, a contrary result if only a tin coating is 
used. 
The tin-zinc coating may contain other metals to modify the physical 
properties of the tin-zinc, two phase metallic coating to contribute to 
the strength of the coating, to the corrosion-resistant properties of the 
coating, the color of the coating, the stability of the coating and the 
coating properties of the coating. The tin-zinc coating can be applied to 
stainless steel, carbon steel and copper materials by preferably using a 
continuous, hot-dip process; however, the coating may be applied by other 
means such as by electroplating, an airknife process, etc. The tin-zinc 
coating is not limited to only the protection of stainless steel, carbon 
steel and copper and may also be applied to other metals such as bronze, 
tin, titanium, etc. Prior to Applicants invention, a two phase metallic 
tin-zinc coating has not been previously used, especially on architectural 
materials such as metallic building and roofing materials. The bonding of 
the tin-zinc coating to carbon steel, stainless steel and copper materials 
is surprisingly strong and forms a durable protective coating which is not 
easily removable, thereby resisting flaking of the coating. 
The surface of the metal material is preferably pretreated prior to 
applying the tin-zinc coating to improve the bonding between the tin-zinc 
coating and the surface of the metal material. For stainless steel 
materials, a pretreatment process should be used which includes 
aggressively pickling and chemically activating the surface of the 
stainless steel to activate the surface thereby providing a significantly 
stronger bonding of the coating. Preferably, the pretreatment process 
disclosed in Assignees' application Ser. No. 000,101 is used. 
The life of the coated metal material is significantly extended by coating 
the material with the tin-zinc metallic coating. The tin-zinc coating acts 
as a barrier to the atmosphere which prevents the metal material from 
oxidizing and/or reducing in the presence of oxygen, carbon dioxide, 
alcohols, halogens or other reducing agents in the environment. Although 
the tin-zinc coating oxidizes in the presence of various reducing agents 
in the atmosphere, the rate of oxidation is significantly slower than that 
of the architectural materials. Furthermore, the tin and zinc oxide which 
forms on the coating surface provides corrosion resistance to the tin-zinc 
coating itself which further enhances the corrosion protection provided by 
the tin-zinc coating. 
The tin-zinc oxides also reduce the reflectivity of the tin-zinc coating 
and color the tin-zinc coating. Terne coated materials have become very 
popular since terne coated materials eventually weather and turn a grey, 
earth tone color. The inventors discovered that the novel tin-zinc 
formulations form a colored coating which closely matches the popular 
grey, earth tone color of weathered terne. Furthermore, by coating the 
building materials with the tin-zinc coating, the usable life of the 
materials is extended typically beyond the life of the structure the 
coated materials are used on due to the corrosion-resistance of the 
tin-zinc coating. 
The tin-zinc coating is primarily composed of tin and zinc and contains 
little, if any, lead thus making the coating essentially lead free and 
environmentally friendly. The lead content, if any, is maintained at 
extremely low levels within the metallic coating. The amount of lead in 
the tin-zinc coating is maintained such that no more than 0.05 weight 
percent is present in the coating. Preferably, the lead content in the 
coating is maintained at levels less than 0.01 weight percent. The 
limiting of lead content in the metallic coating eliminates any concerns 
associated with the leaching of the lead from the metallic coating and the 
environmental concerns associated with products containing lead. 
The tin-zinc metallic coating is a two phase system which contains a large 
weight percentage of tin and zinc. Preferably, the zinc weight percentage 
is at least 7% and over 9% for a two-phase alloy and can be as much as 85% 
of the tin-zinc coating. The tin content within the metallic coating 
essentially makes up the balance of the metallic coating. The tin content 
of the tin-zinc alloy can be from 15-93% of the alloy. Preferably, the tin 
content of the alloy is at least 20 weight percent of the alloy. The tin 
plus zinc content in the alloy is 75 weight percent or more, and 
preferably at least 80 weight percent and more preferably 90 weight 
percent. The coating may contain up to 95 to 100 weight percent tin and 
zinc. The tin-zinc system forms a two phase metallic coating. A two phase 
system is defined as a metal alloy comprising two primary components, i.e. 
tin and zinc. Surprisingly, the inventors have found that the tin-zinc 
coating provides a protective coating with a higher corrosion resistance 
as compared to a tin coating primarily made up of tin. The amount of zinc 
within the metallic coating is maintained so as not to exceed 85% so that 
the metallic coating remains relatively pliable. Preferably, the zinc 
content of the alloy does not exceed 80 weight percent. 
The inventors have discovered that the use of large weight percentages of 
zinc in the tin-zinc alloy does not cause the coating to become too rigid 
or brittle thus preventing the coated material to be formed or bent which 
results in a cracked coating. Extensive experimentation was performed on 
tin-zinc coatings having a zinc content from 7 to 85 weight percent. 
Surprisingly, it was discovered that a tin-zinc coating containing 7-85 
weight percent zinc and essentially the balance tin produced an acceptably 
malleable to be malleable. In addition to the surprising malleability of 
the tin-zinc coating, it was discovered that the coating provides 
comparable and/or superior corrosion resistance to tin, zinc or terne 
coatings. 
It was also discovered that the tin-zinc coating containing 7-85 weight 
percent zinc produced a colored coating which can closely matched the 
gray, earth tone color of weathered terne. Besides terne coatings 
providing corrosion resistance, terne weathers over time and changes color 
to a gray, earth tone color. This color has become very popular with 
consumers; however, the color has been almost impossible until now to 
match unless the material was painted. The inventors have discovered that 
the high zinc tin-zinc coating changes to a color which very closely 
resembles the popular grey, earth tone color. 
The inventors have found that tin-zinc coatings containing 7-85 weight 
percent zinc can be coated by a hot-dip coating process. Tin-zinc coatings 
which contain a high zinc content and/or metal additives can cause the 
alloy to melt at a higher temperature and may require minor modifications 
to a hot-dip process. Such modification may include 1) obtaining a coating 
vat that can handle higher temperatures, and 2) a protective material, 
which floats on the molten alloy to prevent oxidation of the molten alloy 
surface and dross formation on the coated metal material, that will not 
degrade at higher temperatures. 
The tin-zinc coating may contain nickel to increase the corrosion 
resistance of the coating. The nickel in the coating has been found to 
increase the corrosion resistance of the tin-zinc coating especially in 
alcohol and halogen containing environments. The nickel addition to the 
tin-zinc alloy may also positively affect other physical properties of the 
tin-zinc alloy such as act as a metallic stabilizer, resist viscous oxide 
formation of the molten tin-zinc alloy contained in the coating vat, 
and/or reduce dross formation on the coated metal material. The nickel 
content of the tin-zinc coating preferably does not exceed 5.0 weight 
percent. Larger nickel concentrations can make the coated materials 
difficult to form. Typically, the nickel content does not exceed 1.0 
weight percent and is preferably 0.3-0.9 weight percent and more 
preferably about 0.7 weight percent. 
A coloring agent may be added to the tin-zinc alloy to affect the color and 
reflectivity of the coated metal material. Copper metal has been found to 
be an effective coloring agent to reduce the reflectiveness of the newly 
applied tin-zinc coating by dulling the color of the tin-zinc coating. The 
addition of copper to the alloy also improve the corrosion-resistance of 
the alloy, especially in marine environments. The copper addition to the 
tin-zinc alloy may also positively affect other physical properties of the 
tin-zinc alloy such as act as a metallic stabilizer for the tin and/or zinc 
in the alloy, increase the pliability of the tin-zinc alloy, resist viscous 
oxide formation of the molten tin-zinc alloy contained in the coating vat, 
and/or reduce dross formation on the coated metal material. The copper 
content can be added up to 5 weight percent of the two-phase tin-zinc 
alloy. Preferably, the copper content of the alloy does not exceed 2.7 
weight percent of the alloy. If copper is added to the alloy, copper 
content is usually added in amounts from 0.1 to 1.6 weight percent and 
preferably from 1.0 to 1.5 weight percent. Copper is preferably added to 
the molten alloy in the form of brass. 
Magnesium can be added to the tin-zinc alloy to improve the corrosion 
resistance of the tin-zinc alloy. The tin-zinc alloy has anodic 
characteristics which can attract negatively charged components such as 
oxygen, alcohols and halogens. These negatively charged components 
eventually react with the tin-zinc alloy which, in turn, causes the alloy 
to corrode. It has been found that the addition of magnesium to the 
tin-zinc alloy reduces the anodic characteristics of the alloy thus 
increasing the corrosion resistance of the alloy. The addition of 
magnesium also improves the flowability or viscous qualities of the molten 
alloy to improve the ease of applying the coating and uniformity of the 
coating. The addition of magnesium to the molten tin-zinc alloy further 
reduces or eliminates the need of using a flux in the coating process. The 
magnesium content does not exceed 5.0 weight percent of the alloy. The 
magnesium is preferably not more than about 1.0 weight percent of the 
alloy and more preferably, 0.01-0.4 weight percent of the alloy. When only 
magnesium is added to the molten alloy, it is preferably added as pure 
magnesium. 
The tin-zinc alloy may contain titanium. Titanium has been found to 
positively affect the grain refinement of the coated tin-zinc alloy to 
improve the bonding of the tin-zinc alloy to the metal material. A small 
grain size of the alloy has been found to form a stronger bond to the 
metal materials. Titanium in the alloy facilitates in the formation of a 
smaller grain size of the alloy. Titanium has also been found to reduce 
oxidation of the molten alloy and to reduce dross formation. The titanium 
content of the alloy preferably does not exceed 1.0 weight percent of the 
alloy. Preferably, the titanium content of the alloy is from 0.01-0.5%, 
and more preferably 0.01-0.15% of the alloy. If titanium is added to the 
molten tin-zinc alloy, the titanium is preferably added in the form of a 
Zn-Ti alloy. 
Aluminum can be added to the tin-zinc alloy. Aluminum has been found to 
reduce oxidation of the molten alloy and to reduce dross formation. The 
aluminum also improves the bonding of the tin-zinc alloy to the metal 
material. The addition of aluminum reduces the formation of a Fe-Zn 
intermetallic layer thus improving the formability of ferrous metal coated 
materials. Aluminum further increases the luster of the coated tin-zinc 
alloy. In order to dull the color and reflectivity of the tin-zinc coating 
containing aluminum, a coloring and dulling agent such as copper should be 
added to the tin-zinc alloy when aluminum is added to the alloy. The 
amount of aluminum added to the alloy preferably does not exceed 5.0 
weight percent of the alloy. Preferably, the aluminum content of the alloy 
is 0.01-1.0 weight percent, more preferably 0.01-0.5 weight percent and 
even more preferably 0.01-0.3 weight percent. If aluminum is added to the 
alloy, it is preferably added to the molten tin-zinc as an alloy of 
Al-Cu-Mg. 
The tin-zinc metallic coating may also contain small amounts of other 
metallic components which can be used to slightly modify the physical 
properties of the metallic coating. The metallic coating may contain 
bismuth and antimony to increase the strength of the metallic coating and 
also to inhibit the crystallization of the tin at lower temperatures. The 
amount of bismuth in the metallic coating may range between 0-1.7 weight 
percent and the amount of antimony may range between 0-5.5 weight percent 
of the coating. Preferably, antimony and/or bismuth are added to the 
metallic coating in an amount between 0.05-0.5 weight percent of the 
coating. This weight percentage amount is sufficient to prevent the tin 
from crystallizing at low temperatures which may result in the metallic 
coating flaking off the metal materials. It is believed that the high 
levels of zinc also help stabilize the tin within the coating. Antimony 
also improves the corrosion-resistance of the alloy. The addition of 
bismuth improves the mechanical properties of the alloy such as 
pliability, hardness and strength of the alloy. 
Small amounts of other metals, such as iron, may be added to the metallic 
coating to strengthen and/or positively affect other physical properties 
of the tin-zinc alloy. If iron is added to the tin-zinc coating, the iron 
content preferably does not exceed 0.1 weight percent of the alloy. These 
other types of metals typically constitute very small weight percentages 
within the metallic coating and generally do not exceed more than 2% of 
the tin-zinc coating and preferably are less than 1% of the tin-zinc 
coating. 
The tin-zinc coating forms a grey, earth tone color which closely resembles 
the color associated with weathered terne coatings. The grey surface is 
much less reflective than that of coatings of tin and/or non-weathered 
terne. The reduced reflective surface of the tin-zinc coating is important 
in that the coated building materials can be immediately used on facilities 
that require materials not to be highly reflective. Prior coatings such as 
tin and/or terne had to be weathered and/or additionally treated before 
such coated building materials could be used on facilities which prohibit 
the use of highly-reflective materials. The tin-zinc alloy weathers and 
colors quicker than terne or tin coatings. 
The tin-zinc coating can be applied to many types of metal materials. 
Preferably, the metal materials are carbon steel, stainless steel and 
copper. These metal materials are preferably pre-treated before coating to 
clean the material surface and remove oxides from the surface so that a 
strong bond is formed between the metal material and the tin-zinc coating. 
The inventors have also discovered that if the metal material is plated 
with a thin nickel layer prior to coating the metal material with the 
tin-zinc coating, the metal material exhibits improved corrosion 
resistance in acidic and/or halogenic environments. If a nickel layer is 
to be applied, the nickel layer is preferably plated to the metal material 
by an electrolysis process. The thickness of the layer is maintained such 
that it preferably is not more than 3 microns (1.18.times.10.sup.-4 in) 
thick and preferably has a thickness which ranges between 1-3 microns. The 
bond between the tin-zinc coating and the nickel layer is surprisingly 
strong and durable and thereby inhibits the tin-zinc coating from flaking 
especially when the metal materials are preformed or formed during 
installation. The plating of the metal materials with the nickel layer is 
very desirable when the metal materials are used in an environment which 
has high concentrations of fluorine, chlorine and other halogens. Although 
the tin-zinc coating significantly reduces the corrosive effects of 
halogens on the metal materials, it has been found that by placing a thin 
layer of plated nickel between the metal material and the tin-zinc 
coating, the corrosive effects of the halogens are even further reduced. 
The general formulation of the invention is as follows: 
______________________________________ 
Tin 20-93 
Zinc 7-80 
Magnesium 
0.0-5 
Nickel 0.0-5 
Copper 0.0-5 
Titanium 
0.0-1.0 
Aluminum 
0.0-5.0 
Antimony 
0.0-5.5 
Bismuth 0.0-1.7 
Iron 0.0-0.1 
Lead 0.0-0.05 
______________________________________ 
A few examples of the tin-zinc, two-phase metallic coating which have 
exhibited the desired characteristics as mentioned above are set forth as 
follows: 
______________________________________ 
Alloy 
Ingredients 
A B C D E 
______________________________________ 
Tin 20 25 50 60 75 
Magnesium 
&lt;1.0 &lt;1.0 &lt;1.0 &lt;1.0 &lt;1.0 
Nickel .ltoreq.1.0 
.ltoreq.1.0 
.ltoreq.1.0 
.ltoreq.1.0 
.ltoreq.1.0 
Copper .ltoreq.2.7 
.ltoreq.2.7 
.ltoreq.2.7 
.ltoreq.2.7 
.ltoreq.2.7 
Titanium 
&lt;0.5 &lt;0.5 &lt;0.5 &lt;0.5 &lt;0.5 
Aluminum 
&lt;1.0 &lt;1.0 &lt;1.0 &lt;1.0 &lt;1.0 
Antimony 
.ltoreq.5.5 
.ltoreq.5.5 
.ltoreq.5.5 
.ltoreq.5.5 
.ltoreq.5.5 
Bismuth .ltoreq.1.7 
.ltoreq.1.7 
.ltoreq.1.7 
.ltoreq.1.7 
.ltoreq.1.7 
Iron .ltoreq.0.1 
.ltoreq.0.1 
.ltoreq.0.1 
.ltoreq.0.1 
.ltoreq.0.1 
Lead &lt;0.05 &lt;0.05 &lt;0.05 &lt;0.05 &lt;0.05 
______________________________________ 
Typically, the formulations of the tin-zinc metallic coating includes: 
20-80% zinc; 20-80% tin; 0.0-0.4% magnesium; 0.0-1.0% nickel; 0.0-2.7% 
copper; 0.0-0.15% titanium; 0.0-0.5% aluminum; 0.0-5.5 antimony; 0.0-1.5% 
bismuth; up to 0.1% iron and less than 0.01% lead; and preferably 30-65% 
zinc; 35-70% tin; 0.0-0.4% magnesium; 0.0-0.7% nickel; 0.0-1.0% copper; 
0.0-0.15% titanium; 0.0-0.3% aluminum; 0.05-1.0% bismuth and/or antimony; 
less than 0.1% iron; less than 0.01% lead; and the tin plus zinc content 
is at least 90% of the coating. 
The thickness of the tin-zinc coating may be varied depending upon the 
environment in which the metal materials are to be used. The tin-zinc 
coating exhibits superior corrosive-resistant properties as compared to 
tin coatings. The metallic coating may be applied in a thickness between 
0.0003-0.05 in. Preferably, the coating thickness is applied by a 
continuous hot-dip process and ranges between 0.001-0.002 in. Such a 
coating thickness has been found to be adequate to prevent and/or 
significantly reduce the corrosion of the metal materials in virtually all 
types of environments. Coatings having thicknesses greater than 0.002 can 
be used in harsh environments to provide added corrosion protection. 
The tin-zinc coating can be welded with standard lead solders and no-lead 
solders. Preferably, no-lead solders are used to avoid concerns associated 
with the use of lead. 
The invention has been described with reference to the preferred and 
alternate embodiments. Modifications and alterations will become apparent 
to those skilled in the art upon the reading and understanding of the 
details discussed in the detailed discussion of the invention provided for 
herein. This invention is intended to include all such modifications and 
alterations insofar as they come within the scope of the present 
invention.