Standard Test Method for Weight of Coating on Iron Report (Assessment)

In this experiment, we will provide a systematic procedure for establishing the mass of the outside layer (coat) on a zinc-coated steel sheet.

Significance and Use

This experiment offers a standard technique for measuring the weight of a coat on a zinc-coated steel sheet. These results help in determining the amount of zinc to be applied to a metal to prevent rusting. Therefore, consumers will buy these metals based on their specific needs.

Reagents

All tests must use reagent-grade chemicals. All reagents must conform to the set specifications, where such specifications are available. Use other grades only if the reagents are of high purity to allow its use without compromising the accuracy of the experiment.

1. Water—Reagent water used for the preparation of chemical solutions must meet Specification D 1193, Type IV.
2. Dissolve 20g of Sb2O3 or 32 g of SbCl3 in 1000 mL of Hydrochloric Acid to form Antimony Trichloride Solution
3. Concentrated hydrochloric acid (HCl)
4. Add 5 mL of antimony trichloride solution to 100 mL of Hydrochloric acid to form the HCl—Antimony Trichloride Solution
5. Add 500 ml of reagent water to 500 ml of hydrochloric acid, mix and allow it to cool to room temperature.

Precaution

Stibine is a poisonous gas, which may be evolved in small amounts along with hydrogen, has during the HCl – antimony trichloride method. HCl fumes are also present during the stripping process. The test must therefore be done in adequately ventilated environment. It is standard procedure to use a fume hood when experimenting with many samples or when the test is done frequently over a long time (Thompson, Ellison & Wood, 2006).

Sampling

Zinc-Coated Steel Sheets—Selection of samples for determination of weight or mass must be according to Specifications A 653/A 653M, A 792/A 792M, or A 875/ A 875M as per the type of coating (ASTM Standard A90, 2007).

Experimental Procedure

Preliminary Steps

Dilute HCl method is used for stripping zinc alloy coatings containing < 90% zinc shall be done using the dilute hydrochloric acid method. Coatings containing≥ 90 % zinc are stripped using either HCl-antimony trichloride solution or dilute HCl (1 + 1) (alternative standard method).

1. Clean the coated iron or steel sheet with naphtha and then rinse with alcohol according to Huber (2007).
2. Dry thoroughly your sample before measuring your coated iron or steel.
3. Measure the weight of zinc-coated sheets to the nearest 0.01 g.
4. Immerse every specimen individually after measuring weight in the stripping solution and leave it for 15-30 seconds until the violent hydrogen stops and just a few bubbles are being evolved.
5. If sherardized coatings are available, a longer time is required for the reaction to complete.
6. Set the temperature of stripping solution below 100⁰F or 38⁰C (Huber, 2007).
7. Wash the specimens after stripping by scrubbing them under running water, immerse in hot water, and wipe them dry.
8. Measure the weight of the specimens again, to the same precision as in the first measurement (Thompson, Ellison & Wood, 2006).

Results and Calculation

Record all measurements in metric units. Below is a systematic calculation of the weight by the mass of a zinc coat on a sheet.

Zinc-coated Sheet

If the area of the specimen sheet is determined:

C= {(W₁-W₂)/A} x K

Where:

C = weight [mass] of coating, g/m² of sheet,

W₁ = original weight [mass] of specimen, g,

W₂ = weight [mass] of stripped specimen, g,

A = area of sheet, inches² or mm², and

K = a constant = 1.55 x 10³ if A is in inches²= 1 x 10⁶ if A is in mm².

If the area of the specimen sheet is impossible to measure

C= {(W₁-W₂)/ W₂} x T x K

Where:

C = weight [mass] of coating, g/m² of sheet

W₁ = original weight [mass] of the specimen, g,

W₂ = weight [mass] of the stripped specimen, g,

T = thickness of the stripped sheet, inches or mm, and

K = a constant = 1.99 x 10⁵ if T is in inches, = 7.83 x 10³ if T is in mm.

Calculation of Results in Inch-Pound Units

Zinc-coated Sheet

If the area of the specimen sheet is determined:

C= {(W₁-W₂)/A₂} x K

Where:

C = weight [mass] of coating, oz/ft² of sheet,

W₁ = original weight [mass] of specimen, g,

W₂ = weight [mass] of stripped specimen, g,

A = area of sheet, inches² or mm², and,

K = a constant = 5.08 when A is in in.2= 3.28 3 10³ when A is in mm2

If the area of specimen sheet is impossible to measure

C= {(W₁-W₂)/W₂} x T x K

Where:

C = weight [mass] of coating, oz/ft² of sheet,

W₁ = original weight [mass] of specimen, g,

W₂ = weight [mass] of stripped specimen, g,

T = thickness of stripped sheet, inches or mm, and

K = a constant = 652 if T is in inches = 25.7 if T is in mm (ASTM Standard A90, 2007).

Report

Write an experimental report according to standard procedure provided by SOP.

Pre-Experimental Caution

Preservation- It is possible for the specimen to absorb moisture during stripping process (ASTM Standard A90, 2007). Therefore, the protecting agent must not be on the specimen during either of the weight [mass] measurements.

Quality Control

• All documents must ensure that the correct SOP is available, such that documents are correctly approved before issue and that any amendments are properly controlled. These documents should have whole information starting form coated Iron or steel sheet selection, to information relating to measurement on experimental procedure and every observation that can be useful for determine the coating, and time and date when the experiment was carried out.
• All technicians have the duty to make sure that the information in the documents is correct. If any mistakes are found in documents must corrected right away.
• All Controlled paper documents are identified by an authorized signature and held at specified location. Management authorizes electronic documents.

End of Experiment

Prepared by:……………………….

Reviewed and Approved by:……………………………

References

ASTM Standard A90. (2007). Standard test method for weight of coating on iron and steel articles with zinc or zinc-alloy coatings. Web.

Huber, L. (2007). Validation and qualification in analytical laboratories. New York, NY: Prentice Hall.

Thompson, M., Ellison, S. L. & Wood, R. (2006). The international harmonized protocol for the proficiency testing of analytical chemistry laboratories. Journal of Pure and applied Chemistry, 78(1), 1-52.