Acid cleaning agents and related chemicals - Selection,Use, MSDS,Trading - Engineering - http://maxpages.com/jpchemical/MATERIALS_AND

The common problem:
We have scale deposits, which reduce the heat exchange and produce continuous corrosion and metal wastes.
What scale removal to apply?
At which concentration?
At which temperature?
In a bath or under circulation?
How much time is required and under which circulation flow rate?
Which are the dangerous for the installation, for the people, for the environmental?

So why not asking the advise from an expert?
Contact him on line through jpchemical@yahoo.com.
JPCHEMICAL ONLINE provides specification which includes chemical and engineering details of the application procedure
JP CHEMICAL SOLVES PROBLEMS.

General information is given, hereafter, for the acid cleaning agents and related chemicals, which are commonly used by JPCHEMICAL LTD, during chemical cleaning services.
A detailed SPILL RESPONSE is provided, as well as.
The same chemicals can be supplied worldwide, in bulk quantities, on request.
Finally simple MSDS as per STANDARD 16 points of the same chemicals are given.

Hydrochloric acid

For years, the dominant chemical cleaning solvent has been HCl. Typical procedures call for the boiler to be filled with a 5%–10% solution that has been warmed to around 150°F to 160°F. HCl is quite corrosive, so static Soak methods are always employed, although a temporary circulation pump may be used to mix the chemical for a few minutes every hour. Nitrogen bubbling through lower headers also achieves some mixing.
A corrosion Inhibitor must be added to the solution, and typical soak times are limited to a few hours due to potential corrosion of the base metal. Because the chemical is aggressive, it usually removes deposits in just those few hours.
HCl containing 0.25%–1% of ammonium bifluoride (NH4F•HF or ABF) is the preferred solvent for removing siliceous deposits. The ABF is converted to hydrofluoric acid (HF), which is one of the few chemicals that is aggressive toward silicates.
HCl offers several advantages. It is a quick-acting solvent that is aggressive to deposits. It is a good solvent for iron oxide deposits layered with copper, and it is the best solvent for removing silicates. It works well in boilers with small tubes where circulation is restricted. And, it is inexpensive.
However, it is a very corrosive, hazardous chemical. Thus, safety issues are of prime concern.

Hydrochloric acid as per Wikipedia, the free Encyclopedia,, ONE OF THE BEST SITES,
http://en.wikipedia.org/wiki/Hydrochloric_acid, ,

As per Britanica Students Encyclopedia, ONE OF THE BEST INFORMATION SITES,
http://www.britannica.com/ebi/article-9275007

Hydrochloric acid Reactions with metals:
ONE OF THE BEST SITES,,
http://www.gcsechemistry.com/r4.htm

PHOSPHORIC ACID,
As per our favorite Wikipedia Encyclopedia, http://en.wikipedia.org/wiki/Phosphoric_acid,
As per our favorite CHEMICAL OF THE WEEK, http://scifun.chem.wisc.edu/CHEMWEEK/H3PO4/H3PO4.html,

Phosphoric Acid is mainly used as rust removal on iron and carbon steel surfaces

Phosphoric acid may be used by direct application to rusted iron or steel tools or surfaces to convert [[iron(III) oxide]] ([[rust]]) to a water soluble [[phosphate]] compound.

It is usually available as a greenish liquid, suitable for dipping (acid bath), but is more generally used as a component in a gel, commonly called ''Naval jelly''.
As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces.

Care must be taken to avoid acid burns of the skin and especially the eyes, but the residue is easily diluted with water.

When sufficiently diluted can even be nutritious to plant life, containing the essential nutrients phosphorus and iron.

It is sometimes sold under other names, such as "rust remover" or "rust killer".
It should not be directly introduced into surface water such as creeks or into drains, however.

After treatment, the reddish-brown iron oxide will be converted to a black iron phosphate compound that may be scrubbed off.
Multiple applications may be required to remove all rust.
The resultant black compound does not provide any further corrosion resistance (such protection is somewhat provided by the superficially similar [[Parkerize|Parkerizing]] process).

After application and removal of rust using phosphoric acid compounds the metal should be oiled (if to be used bare, as in a tool) or appropriately painted, most durably by using a multiple coat process of primer, intermediate, and finish coats.

>>
Citric Acid
Although the name conjures up an acid-cleaning process, Citric acid is similar to EDTA in that it is a chelant and will bind both iron and copper ions. The citric acid cleaning procedure is similar to the EDTA one. Two citric-based solvents are popular — mono-ammonium and di-ammonium. In the former, the solvent pH is around 3.5 to 4, and the optimum temperature range is 180°F–200°F. Diammmonium Citric acid solutions have a higher pH of about 5 to 6, and this solvent is somewhat less aggressive toward deposits, so a higher temperature (240°F–275°F) is required for it to perform efficiently.
Citric acid is not as strong a chelant as EDTA, and thus is not as popular for post-operational cleanings, although it can be doped with ABF to remove silica deposits. It is sometimes preferred for pre-operational cleanings, where iron oxides constitute the bulk of deposits, and where an aggressive acid Like HCl is not needed. Pre-operational cleaning of HRSGs is one such application.

Sulfamic Acid,
The main use of '''sulfamic acid''' is as a cleaning agent in substitution for hydrochloric acid, in the marine Industry, due to its' safe storage characteristics..

NITRIC ACID

Nitric acid is the traditional acid for the pickling and passivation of stainless steel surfaces.

As per Vicipedia, the excelent free encyclopedia,
http://en.wikipedia.org/wiki/Nitric_acid,

As per Columbia Encyclopedia,
http://www.bartleby.com/65/ni/nitricac.html,

Academic informations and reaction details with metals, as per an excelent site,
http://www.ucc.ie/academic/chem/dolchem/html/comp/nitric.html

CHELATORS

EDTA
Many boilers chemical cleanings are now performed with EDTA. EDTA belongs to a class of compounds known as Chelants.
The most popular procedure uses tetra ammonium EDTA, in which the two hydrogen atoms at the end of each molecule (Four total) are replaced with ammonium (NH4 +) Ions. Ammonia is alkaline, and a typical EDTA cleaning is performed at a pH of 9 to 9.5. Tetra ammonium EDTA is not as aggressive
The advantages of tetra ammonium EDTA includes the following. The chemical Is much less corrosive than HCl and the process is performed at an alkaline pH, so if a bit of residual remains in the Boiler after the cleaning and rinses. It will not attack tubes like HCl will. The chemical itself is not as Hazardous as HCl, although an ammonia smell will be evident.
Among its disadvantages are that the boiler must be fired

Another EDTA choice is the diammonium version, in which the pH of the solvent is adjusted to a range of 5 to 6. This solvent is more reactive than tetra ammonium EDTA, And only needs to be heated to about 200°F to be effective.
However, the lower heating rate reduces the ability of the Chemical to circulate in the boiler.

INHIBITORS

ARMOHIB® CORROSION INHIBITORS APPLICATIONS

Armohib comes in two versions for use with specific acids:
PRODUCT ACID APPLICATIONS.
Armohib 28 Hydrochloric Hydrochloric-Hydrofluoric acid mixtures.
Armohib 31 Sulfuric Sulfamic Citric Phosphoric PHYSICAL PROPERTIES.

Corrosion performance-tested: • 0.25% Armohib 28 in 15% hydrochloric acid at 200°F
Armohib 31 in 15% sulfuric acid at 200°F

Properties:
Armohib Specific Gravity at 25°C Pounds Per Gallons
Appearance at 25°C Pour Point °F
Flash Point °F Cloud Point °F 28 0.925 7.69 Amber Liquid 52 90 31 1.042 8.66 Amber Liquid 24 340 28

APPLICATIONS
There are three major applications for Armohib:
ACID PICKLING
PLANT CLEANING
OILWELL ACIDIZING ACID PICKLING

Pickling is the removal of oxide scales formed during metal working operations by mineral acids. Hydrochloric, phosphoric and sulfuric acids are commonly used. These scales must be removed without undue acid attack on the base metal surface.
An inhibitor is therefore used to protect the cleaned surface, reduce acid wastage and metal loss and prevent pitting and discoloration of the metal. Inhibitors protect weld areas and impede "burning" of the metal, even during temporary shutdown of pickling operations. These inhibitors form a foam blanket preventing heat loss and acid spray.

Amorhib 28 uses:
Hydrochloric acid is used for pickling very high carbon and alloy steels and for wire pickling. Hydrochloric and hydrofluoric acid blends are used to clean ferritic, martensitic and austenitic steels. Iron oxide scale is soluble in hydrochloric acid, and therefore there is no acid attack on the metal surface.
Hydrogen embrittlement is a major problem during pickling of mild steel wire. The addition of Armohib 28 to the hydrochloric acid eliminates or reduces embrittlement. This embrittlement occurs when atomic hydrogen produced by the introduction of the acids, diffuses into the lattices of the metal and strains it. This results in brittleness at the molecular level with no advanced indications such as visible pitting.
The use of Armohib 28 as an inhibitor in hydrochloric acid pickling of steel has no adverse effect on the quality of the metal in subsequent hot dip galvanizing. Tests conducted at an independent laboratory show that the use of Armohib 28 does not have any noticeable influence on the structure of the zinc or the thickness of the zinc layer.

Armorhib 31 uses: Phosphoric acid is used in the surface preparation of structural steel to remove mill scale, rust and contaminants prior to protective surface coating.
Phosphoric acid is of particular value in pickling operations where the scale film is thin, or if the film is a hydrate oxide of iron.

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