Exhibit 31.2

 

**Certifications**

 
|   | I, Brett Gellner, certify that:                                                                                                                                                                                                                                                                                                                                       |
|--------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                                                                                                                                                                                                                                                                                                  |
| 1.     | I have reviewed this annual report on Form 40-F/A of TransAlta   Corporation;                                                                                                                                                                                                                                                                                    |
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| 2.     | Based on my knowledge, this report does not contain any untrue   statement of a material fact or omit to state a material fact necessary to   make the statements made, in light of the circumstances under which such   statements were made, not misleading with respect to the period covered by   this report;                                                    |
|   |                                                                                                                                                                                                                                                                                                                                                                  |
| 3.     | Based on my knowledge, the financial statements, and other financial   information included in this report, fairly present in all material respects   the financial condition, results of operations and cash flows of the issuer   as of, and for, the periods presented in this report;                                                                             |
|   |                                                                                                                                                                                                                                                                                                                                                                  |
| 4.     | The issuer’s other certifying officer(s) and I are responsible   for establishing and maintaining disclosure controls and procedures (as   defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal   control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and   15d-15(f)) for the issuer and have: |
|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
|   |      a)                                                                                                                                                                                                                                                                                                                                      | Designed such disclosure controls and procedures, or caused such   disclosure controls and procedures to be designed under our supervision, to   ensure that material information relating to the issuer, including its   consolidated subsidiaries, is made known to us by others within those   entities, particularly during the period in which this report is being   prepared; |
|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
|   | b)                                                                                                                                                                                                                                                                                                                                                                    | Designed such internal control over financial reporting, or caused   such internal control over financial reporting to be designed under our   supervision, to provide reasonable assurance regarding the reliability of   financial reporting and the preparation of financial statements for external   purposes in accordance with generally accepted accounting principles; |
|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
|   | c)                                                                                                                                                                                                                                                                                                                                                                    | Evaluated the effectiveness of the issuer’s disclosure controls and   procedures and presented in this report our conclusions about the   effectiveness of the disclosure controls and procedures, as of the end of the   period covered by this report based on such evaluation; and |
|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
|   | d)                                                                                                                                                                                                                                                                                                                                                                    | Disclosed in this report any change in the issuer’s internal control   over financial reporting that occurred during the period covered by the   annual report that has materially affected, or is reasonably likely to   materially affect, the issuer’s internal control over financial reporting;   and |
|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
| 5.     | The issuer’s other certifying officer(s) and I have disclosed,   based on our most recent evaluation of internal control over financial   reporting, to the issuer’s auditors and the audit committee of the issuer’s   board of directors (or persons performing the equivalent functions):                                                      |
|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
|   | a)                                                                                                                                                                                                                                                                                                                                                                    | All significant deficiencies and material weaknesses in the design or   operation of internal control over financial reporting which are reasonably   likely to adversely affect the issuer’s ability to record, process, summarize   and report financial information; and |
|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
|   | b)                                                                                                                                                                                                                                                                                                                                                                    | Any fraud, whether or not material, that involves management or other   employees who have a significant role in the issuer’s internal control over   financial reporting. |
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|   |                                                                                                                                                                                                                                                                                                                                                                  |   |
|   | October 30, 2012                                                                                                                                                                                                                                                                                                                                                      |   |
|   |                                                                                                                                                                                                                                                                                                                                                                  | /s/ Brett Gellner |
|   |                                                                                                                                                                                                                                                                                                                                                                  | Brett Gellner |
|   |                                                                                                                                                                                                                                                                                                                                                                  | Chief Financial Officer |
|        |                                                                                                                                                                                                                                                                                                                                                                       |  |  |

 

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